Construction machine control system, construction machine, and method of controlling construction machine

ABSTRACT

A control system controls a construction machine that includes a work machine including a bucket having a plurality of tilting mechanisms. The control system includes: a tilt angle sensor that is provided in the bucket so as to detect tilt angle data including a rotation angle of the bucket about the tilt shaft, the tilt angle sensor being capable of detecting an inclination angle with respect to a horizontal plane; a data acquisition unit to which the tilt angle data is output from the tilt angle sensor; a data fixing unit that fixes the tilt angle data output to the data acquisition unit based on a fixing command to generate fixed data; and a work machine control unit that controls the work machine based on the fixed data until the fixing command is disabled.

FIELD

The present invention relates to a construction machine control system,a construction machine, and a method of controlling a constructionmachine.

BACKGROUND

A construction machine like an excavator includes a work machine thatincludes a boom, an arm, and a bucket. As a method of controlling aconstruction machine, Patent Literatures 1 and 2 disclose limitedexcavation control in which a bucket is moved based on a targetexcavation landform which is a target shape of an excavation object.

CITATION LIST Patent Literature

-   Patent Literature 1: WO 2012/127914 A-   Patent Literature 2: WO 2012/127913 A

SUMMARY Technical Problem

In a construction machine, a tilt bucket that can be tilted is known.The tilt bucket is tilted by a tilt actuator that tilts a bucket inrelation to an arm. In the tilt bucket, tilt angle data of the bucketmay be acquired using a tilt angle sensor. The bucket is inclined inrelation to a horizontal surface according to a raising operation or alowering operation of at least one of a boom and an arm as well as thedriving of the tilt actuator. Thus, it may be difficult for the tiltangle sensor to acquire tilt angle data based on the driving of the tiltactuator due to the raising operation or the lowering operation of atleast one of the boom and the arm. As a result, there is a possibilitythat excavation accuracy decreases and intended construction cannot beexecuted.

An object of some aspects of the present invention is to provide aconstruction machine control system, a construction machine, and amethod of controlling the construction machine capable of suppressing adecrease in excavation accuracy even when a tilt bucket is used.

Solution to Problem

A first aspect of the present invention provides a construction machinecontrol system for a construction machine that includes a work machinecomprising: a boom capable of rotating in relation to a vehicle bodyabout a boom shaft; an arm capable of rotating in relation to the boomabout an arm shaft parallel to the boom shaft; and a bucket capable ofrotating in relation to the arm about each of a bucket shaft parallel tothe arm shaft and a tilt shaft orthogonal to the bucket shaft, thesystem comprising: a tilt angle sensor that is provided in the bucket soas to detect tilt angle data including a rotation angle of the bucketabout at least the tilt shaft, the tilt angle sensor being capable ofdetecting an inclination angle with respect to a horizontal plane; adata acquisition unit to which the tilt angle data is output from thetilt angle sensor; a data fixing unit that fixes the tilt angle dataoutput to the data acquisition unit based on a fixing command togenerate fixed data; and a work machine control unit that controls thework machine based on the fixed data until the fixing command isdisabled.

In the first aspect of the present invention, it is preferable that theconstruction machine control system, further comprises: a firstacquisition unit that acquires dimension data including dimensions ofthe boom, the arm, and the bucket; a second acquisition unit thatacquires target excavation landform data indicating a target excavationlandform which is a target shape of an excavation object; a thirdacquisition unit that acquires work machine angle data including boomangle data indicating a rotation angle of the boom about the boom shaft,arm angle data indicating a rotation angle of the arm about the armshaft, and bucket angle data indicating a rotation angle of the bucketabout the bucket shaft; and a calculation unit that calculates bucketposition data indicating a present position of the bucket based on thework machine angle data, the dimension data, and the fixed data, whereinthe work machine control unit determines a speed limit according to adistance between the bucket and the target excavation landform based onthe target excavation landform data and the bucket position data andexecutes limited excavation control so that a speed in a direction inwhich the work machine approaches the target excavation landform isequal to or smaller than the speed limit, and the fixing command isoutput to the data fixing unit so that the work machine is controlledbased on the fixed data in at least a portion of a period in which thelimited excavation control is executed.

In the first aspect of the present invention, it is preferable that thefixing command is output to the data fixing unit when the limitedexcavation control starts and is disabled when the limited excavationcontrol ends.

In the first aspect of the present invention, it is preferable that theconstruction machine control system, further comprises: a drivinginhibiting unit that inhibits driving of the bucket in the limitedexcavation control.

In the first aspect of the present invention, it is preferable that theconstruction machine control system, further comprises: an operatingdevice that outputs an operation signal for operating a hydrauliccylinder capable of driving the bucket, wherein the driving inhibitingunit disables the operation signal output from the operating device.

In the first aspect of the present invention, it is preferable that theconstruction machine control system, further comprises: a fourthacquisition unit that acquires shape data of the bucket, wherein thetarget excavation landform data is 2-dimensional target shape of theexcavation object in a working plane orthogonal to the bucket shaft, thecalculation unit calculates 2-dimensional bucket data which indicates anouter shape of the bucket in the working plane and includes the bucketposition data based on the work machine angle data, the dimension data,the shape data, and the fixed data, and the work machine control unitcontrols the work machine based on the 2-dimensional bucket data.

In the first aspect of the present invention, it is preferable that thecalculation unit calculates a relative position between the bucket andthe target excavation landform based on the 2-dimensional bucket data,vehicle body position data indicating a present position of the vehiclebody, and vehicle body attitude data indicating an attitude of thevehicle body.

A second aspect of the present invention provides a construction machinecomprising: a lower traveling structure; an upper revolving structurethat is supported by the lower traveling structure; a work machine thatincludes a boom, an arm and a bucket and is supported by the upperrevolving structure; and the control system according to the firstaspect of the present invention.

A third aspect of the present invention provides a method of controllinga construction machine that includes a work machine comprising: a boomcapable of rotating in relation to a vehicle body about a boom shaft; anarm capable of rotating in relation to the boom about an arm shaftparallel to the boom shaft; and a bucket capable of rotating in relationto the arm about a bucket shaft parallel to the arm shaft and a tiltshaft orthogonal to the bucket shaft, the method comprising: detectingtilt angle data indicating a rotation angle of the bucket about the tiltshaft using a tilt angle sensor that is provided in the bucket and thatcan detect an inclination angle with respect to a horizontal plane;acquiring the tilt angle data output from the tilt angle sensor; fixingthe tilt angle data based on a fixing command to generate fixed data;and controlling the work machine based on the fixed data until thefixing command is disabled.

Advantageous Effects of Invention

According to the aspects of the present invention, a decrease inexcavation accuracy is suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating an example of a constructionmachine.

FIG. 2 is a side sectional view illustrating an example of a bucket.

FIG. 3 is a front view illustrating an example of a bucket.

FIG. 4 is a side view schematically illustrating an example of theconstruction machine.

FIG. 5 is a rear view schematically illustrating an example of theconstruction machine.

FIG. 6 is a plan view schematically illustrating an example of theconstruction machine.

FIG. 7 is a side view schematically illustrating an example of a bucket.

FIG. 8 is a front view schematically illustrating an example of thebucket.

FIG. 9 is a block diagram illustrating an example of a control system.

FIG. 10 is a diagram illustrating an example of a hydraulic cylinder.

FIG. 11 is a diagram illustrating an example of a stroke sensor.

FIG. 12 is a diagram for describing an example of limited excavationcontrol.

FIG. 13 is a diagram illustrating an example of a hydraulic system.

FIG. 14 is a diagram illustrating an example of a hydraulic system.

FIG. 15 is a diagram illustrating an example of a hydraulic system.

FIG. 16 is a flowchart illustrating an example of a method ofcontrolling a construction machine.

FIG. 17A is a functional block diagram illustrating an example of acontrol system.

FIG. 17B is a functional block diagram illustrating an example of acontrol system.

FIG. 18 is a diagram for describing an example of limited excavationcontrol.

FIG. 19 is a diagram schematically illustrating an example of a bucket.

FIG. 20 is a diagram schematically illustrating an example of a bucket.

FIG. 21 is a diagram schematically illustrating an example of a bucket.

FIG. 22 is a diagram schematically illustrating an example of a bucket.

FIG. 23 is a diagram schematically illustrating an example of a workmachine.

FIG. 24 is a diagram schematically illustrating an example of a bucket.

FIG. 25 is a schematic diagram for describing an example of a method ofcontrolling a construction machine.

FIG. 26 is a flowchart illustrating an example of limited excavationcontrol.

FIG. 27 is a diagram for describing an example of limited excavationcontrol.

FIG. 28 is a diagram for describing an example of limited excavationcontrol.

FIG. 29 is a diagram for describing an example of limited excavationcontrol.

FIG. 30 is a diagram for describing an example of limited excavationcontrol.

FIG. 31 is a diagram for describing an example of limited excavationcontrol.

FIG. 32 is a diagram for describing an example of limited excavationcontrol.

FIG. 33 is a diagram for describing an example of limited excavationcontrol.

FIG. 34 is a diagram for describing an example of limited excavationcontrol.

FIG. 35 is a schematic diagram for describing an example of a method ofcontrolling a construction machine.

FIG. 36 is a schematic diagram illustrating an example of a tilt anglesensor.

FIG. 37 is a diagram illustrating an example of a hydraulic system.

FIG. 38 is a diagram illustrating an example of a display unit.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments according to the present invention aredescribed with reference to the drawings, and the present invention isnot limited thereto. Constituent components of the respectiveembodiments described hereinafter may be appropriately combined witheach other. Moreover, some constituent components may be not used.

In the following description, a global coordinate system and a localcoordinate system are set and the positional relation of respectiveportions will be described with reference to these coordinate systems.The global coordinate system is a coordinate system based on an originPr (see FIG. 4) fixed to the earth. The local coordinate system is acoordinate system based on an origin P0 (see FIG. 4) fixed to a vehiclebody 1 of a construction machine CM. The local coordinate system may bereferred to as a vehicle body coordinate system.

In the following description, the global coordinate system isrepresented by an XgYgZg orthogonal coordinate system. As will bedescribed later, the reference position (origin) Pg of the globalcoordinate system is positioned in a work area. A direction within ahorizontal plane is defined as an Xg-axis direction, a directionorthogonal to the Xg-axis direction within the horizontal plane isdefined as a Yg-axis direction, and a direction orthogonal to theXg-axis direction and the Yg-axis direction is defined as a Zg-axisdirection. Moreover, rotational (inclination) directions about the Xg,Yg, and Zg-axes are defined as θXg, θYg, and θZg-directions,respectively. The Xg-axis is orthogonal to a YgZg plane. The Yg-axis isorthogonal to an XgZg plane. The Zg-axis is orthogonal to an XgYg plane.The XgYg plane is parallel to the horizontal plane. The Zg-axisdirection is a vertical direction.

In the following description, the local coordinate system is representedby an XYZ orthogonal coordinate system. As will be described later, thereference position (origin) P0 of the local coordinate system ispositioned at the revolution center AX of a revolving structure 3. Adirection within a certain plane is defined as an X-axis direction, adirection orthogonal to the X-axis direction within the plane is definedas a Y-axis direction, and a direction orthogonal to the X-axisdirection and the Y-axis direction is defined as a Z-axis direction.Moreover, rotational (inclination) directions about the X, Y, and Z-axesare defined as θX, θY, and θZ-directions, respectively. The X-axis isorthogonal to the YZ plane. The Y-axis is orthogonal to the XZ plane.The Z-axis is orthogonal to the XY plane.

[Overall Structure of Excavator]

FIG. 1 is a perspective view illustrating an example of a constructionmachine CM according to the present embodiment. In the presentembodiment, an example in which the construction machine CM is anexcavator CM that includes a work machine 2 operating with hydraulicpressure.

As illustrated in FIG. 1, the excavator CM includes the vehicle body 1and the work machine 2. As will be described later, a control system 200that executes excavation control is mounted on the excavator CM.

The vehicle body 1 includes the revolving structure 3, a cab 4, and atraveling device 5. The revolving structure 3 is disposed on thetraveling device 5. The traveling device 5 supports the revolvingstructure 3. The revolving structure 3 may be referred to as an upperrevolving structure 3. The traveling device 5 may be referred to as alower traveling structure 5. The revolving structure 3 can revolve abouta revolution axis AX. A driver's seat 4S on which an operator sits isprovided in the cab 4. The operator operates the excavator CM in the cab4. The traveling device 5 includes a pair of crawler belts 5Cr. Withrotation of the crawler belts 5Cr, the excavator CM travels. Thetraveling device 5 may include wheels (tires).

In the present embodiment, a positional relation of respective portionsis described based on the driver's seat 4S. A front-rear direction isdefined based on the driver's seat 4S. A left-right direction is definedbased on the driver's seat 4S. The left-right direction is identical toa vehicle width direction. A direction in which the driver's seat 4Sfaces the front is defined as a front direction and a direction oppositeto the front direction is defined as a rear direction. The right andleft sides in a lateral direction when the driver's seat 4S faces thefront are defined as right and left directions, respectively. In thepresent embodiment, the front-rear direction is the X-axis direction andthe left-right direction is the Y-axis direction. The direction in whichthe driver's seat 4S faces the front is the front direction (+Xdirection) and the direction opposite to the front direction is the reardirection (−X direction). One direction of the vehicle width directionwhen the driver's seat 4S faces the front is the right direction (+Ydirection) and the other direction of the vehicle width direction is theleft direction (−Y direction).

The revolving structure 3 includes an engine room 9 in which an engineis stored and a counterweight provided at the rear portion of therevolving structure 3. A handrail 19 is provided in a portion of therevolving structure 3 on the front side of the engine room 9. An engine,a hydraulic pump, and the like are disposed in the engine room 9.

The work machine 2 is connected to the revolving structure 3. The workmachine 2 includes a boom 6 connected to the revolving structure 3 witha boom pin 13 interposed, an arm 7 connected to the boom 6 with an armpin 14 interposed, a bucket 8 connected to the arm 7 with a bucket pin15 and a tilt pin 80 interposed, a boom cylinder 10 driving the boom 6,an arm cylinder 11 driving the arm 7, a bucket cylinder 12 driving thebucket 8, and a tilt cylinder 30. A base end (boom foot) of the boom 6is connected to the revolving structure 3. A distal end (boom top) ofthe boom 6 is connected to a base end (arm foot) of the arm 7. A distalend (arm top) of the arm 7 is connected to a base end of the bucket 8.The boom cylinder 10, the arm cylinder 11, the bucket cylinder 12, andthe tilt cylinder 30 are hydraulic cylinders driven by operating oil.

The work machine 2 includes a first stroke sensor 16 disposed in theboom cylinder 10 so as to detect a stroke length (boom cylinder length)of the boom cylinder 10, a second stroke sensor 17 disposed in the armcylinder 11 so as to detect a stroke length (arm cylinder length) of thearm cylinder 11, and a third stroke sensor 18 disposed in the bucketcylinder 12 so as to detect a stroke length (bucket cylinder length) ofthe bucket cylinder 12.

The boom 6 can rotate about a boom shaft J1 which is a rotating shaft inrelation to the revolving structure 3. The arm 7 can rotate about an armshaft J2 which is a rotating shaft parallel to the boom shaft J1 inrelation to the boom 6. The bucket 8 can rotate about a bucket shaft J3which is a rotating shaft parallel to the boom shaft J1 and the armshaft J2 in relation to the arm 7. The bucket 8 can rotate about a tiltshaft J4 which is a rotating shaft orthogonal to the bucket shaft J3 inrelation to the arm 7. The boom pin 13 includes the boom shaft J1. Thearm pin 14 includes the arm shaft J2. The bucket pin 15 includes abucket shaft J3. The tilt pin 80 includes the tilt shaft J4.

In the present embodiment, the boom shaft J1, the arm shaft J2, and thebucket shaft J3 are parallel to the Y-axis. The boom 6, the arm 7, andthe bucket 8 can rotate in the θY-direction. In the present embodiment,the XZ plane includes a so-called vertical rotation plane of the boom 6and the arm 7.

In the following description, the stroke length of the boom cylinder 10will be appropriately referred to as a boom cylinder length or a boomstroke, the stroke length of the arm cylinder 11 will be appropriatelyreferred to as an arm cylinder length or an arm stroke, the strokelength of the bucket cylinder 12 will be appropriately referred to as abucket cylinder length or a bucket stroke, and the stroke length of thetilt cylinder 30 will be appropriately referred to as a tilt cylinderlength. Moreover, in the following description, the boom cylinderlength, the arm cylinder length, the bucket cylinder length, and thetilt cylinder length will be appropriately collectively referred to ascylinder length data L.

[Bucket]

Next, the bucket 8 according to the present embodiment will bedescribed. FIG. 2 is a side sectional view illustrating an example ofthe bucket 8 according to the present embodiment. FIG. 3 is a front viewillustrating an example of the bucket 8 according to the presentembodiment. In the present embodiment, the bucket 8 is a tilt bucket.

As illustrated in FIGS. 2 and 3, the work machine 2 has the bucket 8that can rotate in relation to the arm 7 about the bucket shaft J3 andthe tilt shaft J4 orthogonal to the bucket shaft J3. The bucket 8 isrotatably supported by the arm 7 about the bucket pin 15 (bucket shaftJ3). The bucket 8 is rotatably supported by the arm 7 about the tilt pin80 (the tilt shaft J4). The bucket shaft J3 and the tilt shaft J4 areorthogonal to each other. The bucket 8 is rotatably supported by the arm7 about the bucket shaft J3 and the tilt shaft J4 orthogonal to thebucket shaft J3.

The bucket 8 is connected to the distal end of the arm 7 with aconnection member (an underframe) 90 interposed. The bucket pin 15connects the arm 7 and the connection member 90. The tilt pin 80connects the connection member 90 and the bucket 8. The bucket 8 isrotatably connected to the arm 7 with the connection member 90interposed.

The bucket 8 includes a bottom plate 81, a back plate 82, a top plate83, a side plate 84, and a side plate 85. The bottom plate 81, the topplate 83, the side plate 84, and the side plate 85 form an opening 86 ofthe bucket 8.

The bucket 8 has a bracket 87 provided in an upper portion of the topplate 83. The bracket 87 is provided at an anteroposterior position ofthe top plate 83. The bracket 87 is connected to the connection member90 and the tilt pin 80.

The connection member 90 includes a plate member 91, a bracket 92provided on an upper surface of the plate member 91, and a bracket 93provided on a lower surface of the plate member 91. The bracket 92 isconnected to the arm 7 and a second link pin 95 (described later). Thebracket 93 is provided in an upper portion of the bracket 87 and isconnected to the tilt pin 80 and the bracket 87.

The bucket pin 15 connects the bracket 92 of the connection member 90and the distal end of the arm 7. The tilt pin 80 connects the bracket 93of the connection member 90 and the bracket 87 of the bucket 8. Due tothis, the connection member 90 and the bucket 8 can rotate about thebucket shaft J3 in relation to the arm 7 and the bucket 8 can rotateabout the tilt shaft J4 in relation to the connection member 90.

The work machine 2 includes a first link member 94 that is rotatablyconnected to the arm 7 with a first link pin 94P interposed and a secondlink member 95 that is rotatably connected to the bracket 92 with asecond link pin 95P interposed. A base end of the first link member 94is connected to the arm 7 with the first link pin 94P interposed. A baseend of the second link member 95 is connected to the bracket 92 with thesecond link pin 95P interposed. The distal end of the first link member94 and the distal end of the second link member 95 are connected by abucket cylinder top pin 96.

The distal end of the bucket cylinder 12 is rotatably connected to thedistal end of the first link member 94 and the distal end of the secondlink member 95 with the bucket cylinder top pin 96 interposed. When thebucket cylinder 12 is operated so as to be extended and retracted, theconnection member 90 rotates about the bucket shaft J3 together with thebucket 8.

The tilt cylinder 30 is connected to a bracket 97 provided in theconnection member 90 and a bracket 88 provided in the bucket 8. The rodof the tilt cylinder 30 is connected to the bracket 97 with a pininterposed. The body portion of the tilt cylinder 30 is connected to thebracket 88 with the pin interposed. When the bucket cylinder 30 isoperated so as to be extended and retracted, the bucket 8 rotates aboutthe tilt shaft J4.

In this manner, the bucket 8 rotates about the bucket shaft J3 accordingto the operation of the bucket cylinder 12. The bucket 8 rotates aboutthe tilt shaft J4 according to the operation of the tilt cylinder 30. Inthe present embodiment, the tilt pin 80 (the tilt shaft J4) rotates(inclines) together with the bucket 8 according to the rotation of thebucket 8 about the bucket shaft J3.

In the present embodiment, the work machine 2 includes a tilt anglesensor 70 that detects tilt angle data indicating a rotation angle δ ofthe bucket 8 about the tilt shaft J4. The tilt angle sensor 70 detects atilt angle (rotation angle) of the bucket 8 in relation to thehorizontal plane of the global coordinate system. The tilt angle sensor70 is a so-called biaxial angle sensor and detects inclination angles inrelation to the two θXg and θYg directions described later. The tiltangle sensor 70 is provided in at least a portion of the bucket 8. Thetilt angle in the global coordinate system is converted to a tilt angleδ in the local coordinate system based on a detection result of aninclination sensor 24.

The bucket 8 is not limited to the present embodiment. The inclinationangle (tilt angle) of the bucket 8 may be set optionally. Another axismay be added to the axes of the inclination angles.

[Structure of Excavator]

FIG. 4 is a side view schematically illustrating the excavator CMaccording to the present embodiment. FIG. 5 is a rear view schematicallyillustrating the excavator CM according to the present embodiment. FIG.6 is a plan view schematically illustrating the excavator CM accordingto the present embodiment.

In the present embodiment, the distance L1 between the boom shaft J1 andthe arm shaft J2 is referred to as a boom length L1. The distance L2between the arm shaft J2 and the bucket shaft J3 is referred to as anarm length L2. The distance L3 between the bucket shaft J3 and a distalend 8 a of the bucket 8 is referred to as a bucket length L3.

The distal end of the bucket 8 includes a distal end of a tooth of thebucket 8. In the present embodiment, the distal end of the tooth of thebucket 8 has a straight shape. The bucket 8 may have a plurality ofsharp teeth. In the following description, the distal ends 8 a of thebucket 8 will be appropriately referred to as cutting edges 8 a.

The excavator CM has an angle detection device 22 that detects the angleof the work machine 2. The angle detection device 22 detects workmachine angle data including boom angle data indicating a rotation angleα of the boom 6 about the boom shaft J1, arm angle data indicating arotation angle β of the arm 7 about the arm shaft J2, and bucket angledata indicating a rotation angle γ of the bucket 8 about the bucketshaft J3. In the present embodiment, the boom angle (rotation angle) αincludes an inclination angle of the boom 6 in relation to the axisparallel to the Z-axis of the local coordinate system. The arm angle(rotation angle) β includes an inclination angle of the arm 7 inrelation to the boom 6. The bucket angle (rotation angle) γ includes aninclination angle of the bucket 8 in relation to the arm 7.

In the present embodiment, the angle detection device 22 includes thefirst stroke sensor 16 disposed in the boom cylinder 10, the secondstroke sensor 17 disposed in the arm cylinder 11, and the third strokesensor 18 disposed in the bucket cylinder 12. The boom cylinder lengthis calculated based on a detection result of the first stroke sensor 16.The arm cylinder length is calculated based on a detection result of thesecond stroke sensor 17. The bucket cylinder length is calculated basedon a detection result of the third stroke sensor 18. In the presentembodiment, when the boom cylinder length is detected by the firststroke sensor 16, the boom angle α is derived or calculated. When thearm cylinder length is detected by the second stroke sensor 17, the armangle β is derived or calculated. When the bucket cylinder length isdetected by the third stroke sensor 18, the bucket angle γ is derived orcalculated.

The excavator CM includes a position detection device 20 capable ofdetecting vehicle body position data P indicating the present positionof the vehicle body 1 and vehicle body attitude data Q indicating theattitude of the vehicle body 1. The present position of the vehicle body1 includes the present position (Xg, Yg, and Zg positions) of thevehicle body 1 in the global coordinate system. The attitude of thevehicle body 1 includes the position of the revolving structure 3 inrelation to the θXg, θYg, and θZg directions. The attitude of thevehicle body 1 includes an inclination angle (roll angle) θ1 in theleft-right direction of the revolving structure 3 in relation to thehorizontal plane (XgYg plane), an inclination angle (pitch angle) θ2 inthe front-rear direction of the revolving structure 3 in relation to thehorizontal plane, and an angle (yaw angle) θ3 between the referencedirection (for example, the north) of the global coordinate and thedirection in which the revolving structure 3 (the work machine 2) faces.

The position detection device 20 includes an antenna 21, a positionsensor 23, and the inclination sensor 24. The antenna 21 is an antennafor detecting the present position of the vehicle body 1. The antenna 21is a global navigation satellite systems (GNSS) antenna. The antenna 21is a real time kinematic-global navigation satellite systems (RTK-GNSS)antenna. The antenna 21 is provided in the revolving structure 3. In thepresent embodiment, the antenna 21 is provided in the handrail 19 of therevolving structure 3. The antenna 21 may be provided in a reardirection of the engine room 9. For example, the antenna 21 may beprovided in the counterweight of the revolving structure 3. The antenna21 outputs a signal corresponding to a received radio wave (GNSS radiowave) to the position sensor 23.

The position sensor 23 includes a 3-dimensional position sensor and aglobal coordinate calculating unit and detects an installed position Prof the antenna 21 in the global coordinate system. The global coordinatesystem is a 3-dimensional coordinate system based on the referenceposition Pg provided in a work area. As illustrated in FIG. 4, in thepresent embodiment, the reference position Pg is the position of thedistal end of a reference post set in the work area.

In the present embodiment, the antenna 21 includes a first antenna 21Aand a second antenna 21B provided in the revolving structure 3 so as tobe separated in the Y-axis direction (the vehicle width direction of therevolving structure 3) of the local coordinate system. The positionsensor 23 detects an installed position Pra of the first antenna 21A andan installed position Prb of the second antenna 21B.

The position detection device 20 acquires the vehicle body position dataP and the vehicle body attitude data Q in the global coordinate usingthe position sensor 23. The vehicle body position data P is dataindicating the reference position P0 positioned at the revolution axis(revolution center) AX of the revolving structure 3. The referenceposition data P may be data indicating the installed position Pr. Theposition detection device 20 acquires the vehicle body position data Pincluding the reference position P0. Moreover, the position detectiondevice 20 acquires the vehicle body attitude data Q based on the twoinstalled positions Pra and Prb. The vehicle body attitude data Q isdetermined based on an angle between a reference direction (for example,the north) of the global coordinate and a line determined by theinstalled positions Pra and Prb. The vehicle body attitude data Qindicates a direction in which the revolving structure 3 (the workmachine 2) faces.

The inclination sensor 24 is provided in the revolving structure 3. Theinclination sensor 24 includes an inertial measurement unit (IMU). Theinclination sensor 24 is disposed under the cab 4. A high-rigidity frameis disposed in a portion of the revolving structure 3 under the cab 4.The inclination sensor 24 may be disposed on a lateral side (right orleft side) of the revolution axis AX (the reference position P2) of therevolving structure 3. The inclination sensor 24 is disposed in theframe. The position detection device 20 acquires the vehicle bodyattitude data Q including the roll angle θ1 and the pitch angle θ2 usingthe inclination sensor 24.

FIG. 7 is a side view schematically illustrating the bucket 8 accordingto the present embodiment. FIG. 8 is a front view schematicallyillustrating the bucket 8 according to the present embodiment.

In the present embodiment, the distance L4 between the bucket shaft J3and the tilt shaft J4 is referred to as a tilt length L4. The distanceL5 between the side plate 84 and the side plate 85 is referred to as awidth dimension L5 of the bucket 8. The tilt angle δ is an inclinationangle of the bucket 8 in relation to the XY plane. The tilt angle dataindicating the tilt angle δ is derived from the detection result of thetilt angle sensor 70. The tilt shaft angle c is an inclination angle ofthe tilt shaft J4 (the tilt pin 80) in relation to the XY plane. Thetilt angle data indicating the tilt shaft angle c is derived from thedetection result of the angle detection device 22.

In the present embodiment, although the tilt angle data is acquired fromthe detection result of the angle detection device 22, the tilt angle ofthe bucket 8 may be calculated and acquired from the result of detectionof the stroke length (tilt cylinder length) of the tilt cylinder 30, forexample.

[Configuration of Control System]

Next, an overview of the control system 200 according to the presentembodiment will be described. FIG. 9 is a block diagram illustrating afunctional configuration of the control system 200 according to thepresent embodiment.

The control system 200 controls an excavation process of using the workmachine 2. The control of excavation process includes limited excavationcontrol. As illustrated in FIG. 9, the control system 200 includes theposition detection device 20, the angle detection device 22, the tiltangle sensor 70, an operating device 25, a work machine controller 26, apressure sensor 66, a control valve 27, a direction control valve 64, adisplay controller 28, a display unit 29, an input unit 36, a sensorcontroller 32, a pump controller 34, and an IMU 24.

The display unit 29 displays predetermined information such as a targetexcavation landform that is to be excavated based on control of thedisplay controller 28. The input unit 36 is configured as a touch panelthat inputs data to the display unit and is operated by an operator.When operated by the operator, the input unit 36 generates an operationsignal based on the operation and outputs the operation signal to thedisplay controller 28.

The operating device 25 is disposed in the cab 4. The operating device25 is operated by the operator. The operating device 25 receives anoperator operation that drives the work machine 2. In the presentembodiment, the operating device 25 is a pilot hydraulic-type operatingdevice.

In the following description, oil supplied to hydraulic cylinders (theboom cylinder 10, the arm cylinder 11, the bucket cylinder 12, and thetilt cylinder 30) in order to operate the hydraulic cylinders will beappropriately referred to as operating oil. In the present embodiment,the amount of operating oil supplied to the hydraulic cylinder isadjusted by the direction control valve 64. The direction control valve64 operates with oil supplied. In the following description, oilsupplied to the direction control valve 64 in order to operate thedirection control valve 64 will be appropriately referred to as pilotoil. Moreover, the pressure of pilot oil will be appropriately referredto as pilot pressure.

The operating oil and the pilot oil may be delivered from the samehydraulic pump. For example, a portion of the operating oil deliveredfrom the hydraulic pump is decompressed by a pressure-reducing valve andthe decompressed operating oil may be used as the pilot oil. Moreover, ahydraulic pump (main hydraulic pump) that delivers operating oil and ahydraulic pump (pilot hydraulic pump) that delivers pilot oil may bedifferent hydraulic pumps.

The operating device 25 includes a first operating lever 25R, a secondoperating lever 25L, and a third operating lever 25P. The firstoperating lever 25R is disposed on the right side of the driver's seat4S, for example. The second operating lever 25L is disposed on the leftside of the driver's seat 4S, for example. The third operating lever 25Pis disposed in the second operating lever 25L, for example. The thirdoperating lever 25P may be disposed in the first operating lever 25R. Inthe first and second operating levers 25R and 25L, the front-rear andleft-right movements correspond to 2-axis operations.

The boom 6 and the bucket 8 are operated by the first operating lever25R. The operation in the front-rear direction of the first operatinglever 25R corresponds to an operation of the boom 6, and a loweringoperation and a raising operation of the boom 6 are executed accordingto the operation in the front-rear direction. The operation in theleft-right direction of the first operating lever 25R corresponds to anoperation of the bucket 8, and an excavating operation and a releasingoperation of the bucket 8 are executed according to the operation in theleft-right direction.

The arm 7 and the revolving structure 3 are operated by the secondoperating lever 25L. The operation in the front-rear direction of thesecond operating lever 25L corresponds to an operation of the arm 7, anda raising operation and a lowering operation of the arm 7 are executedaccording to the operation in the front-rear direction. The operation inthe left-right direction of the second operating lever 25L correspondsto revolving of the revolving structure 3, and a right revolvingoperation and a left revolving operation of the revolving structure 3are executed according to the operation in the left-right direction.

The bucket 8 is operated by the third operating lever 25P. In thepresent embodiment, rotation of the bucket 8 about the bucket shaft J3is operated by the first operating lever 25R. Rotation (tilting) of thebucket 8 about the tilt shaft J4 is operated by the third operatinglever 25P.

In the present embodiment, the raising operation of the boom 6corresponds to a dumping operation. The lowering operation of the boom 6corresponds to an excavating operation. The lowering operation of thearm 7 corresponds to an excavating operation. The raising operation ofthe arm 7 corresponds to a dumping operation. The lowering operation ofthe bucket 8 corresponds to an excavating operation. The loweringoperation of the arm 7 may be referred to as a bending operation. Theraising operation of the arm 7 may be referred to as an extendingoperation.

The pilot oil which has been delivered from the pilot hydraulic pump anddecompressed to pilot pressure by the control valve is supplied to theoperating device 25. The pilot pressure is adjusted by the amount ofoperation of the operating device 25, and the direction control valve 64via which operating oil supplied to the hydraulic cylinders (the boomcylinder 10, the arm cylinder 11, the bucket cylinder 12, and the tiltcylinder 40) is driven with the pilot pressure. The pressure sensor 66is disposed in pilot pressure lines 450. The pressure sensor 66 detectsthe pilot pressure. The detection result of the pressure sensor 66 isoutput to the work machine controller 26.

The first operating lever 25R is operated in the front-rear direction inorder to drive the boom 6. The direction control valve 64 via which theoperating oil supplied to the boom cylinder 10 for driving the boom 6 isdriven according to an amount of operation (amount of boom operation) ofthe first operating lever 25R in the front-rear direction.

The first operating lever 25R is operated in the left-right direction inorder to drive the bucket 8. The direction control valve 64 via whichthe operating oil supplied to the bucket cylinder 12 for driving thebucket 8 is driven according to the amount of operation (amount ofbucket operation) of the first operating lever 25R in the left-rightdirection.

The second operating lever 25L is operated in the front-rear directionin order to drive the arm 7. The direction control valve 64 via whichthe operating oil supplied to the arm cylinder 11 for driving the arm 7is driven according to an amount of operation (amount of arm operation)of the second operating lever 25L in the front-rear direction.

The second operating lever 25L is operated in the left-right directionin order to drive the revolving structure 3. The direction control valve64 via which the operating oil supplied to a hydraulic actuator fordriving the revolving structure 3 is driven according to the amount ofoperation of the second operating lever 25L in the left-right direction.

The third operating lever 25P is operated in order to drive the bucket 8(rotate the same about the tilt shaft J4). The direction control valve64 via which the operating oil supplied to the tilt cylinder 30 fortilting the bucket 8 is driven according to the amount of operation ofthe third operating lever 25P.

The operation in the left-right direction of the first operating lever25R may correspond to the operation of the boom 6, and the operation inthe front-rear direction may correspond to the operation of the bucket8. The operation in the left-right direction of the second operatinglever 25L may correspond to the operation of the arm 7, and theoperation in the front-rear direction may correspond to the operation ofthe revolving structure 3.

The control valve 27 operates in order to adjust the amount of operatingoil supplied to the hydraulic cylinders (the boom cylinder 10, the armcylinder 11, the bucket cylinder 12, and the tilt cylinder 30). Thecontrol valve 27 operates based on a control signal from the workmachine controller 26.

The angle detection device 22 detects the work machine angle dataincluding the boom angle data indicating the rotation angle α of theboom 6 about the boom shaft J1, the arm angle data indicating therotation angle β of the arm 7 about the arm shaft J2, and the bucketangle data indicating the rotation angle γ of the bucket 8 about thebucket shaft J3.

In the present embodiment, the angle detection device 22 includes thefirst stroke sensor 16, the second stroke sensor 17, and the thirdstroke sensor 18. The detection result of the first stroke sensor 16,the detection result of the second stroke sensor 17, and the detectionresult of the third stroke sensor 18 are output to the sensor controller32. The sensor controller 32 calculates the boom cylinder length basedon the detection result of the first stroke sensor 16. The first strokesensor 16 outputs a phase shift pulse associated with the revolvingoperation to the sensor controller 32. The sensor controller 32calculates the boom cylinder length based on the phase shift pulseoutput from the first stroke sensor 16. Similarly, the sensor controller32 calculates the arm cylinder length based on the detection result ofthe second stroke sensor 17. The sensor controller 32 calculates thebucket cylinder length based on the detection result of the third strokesensor 18.

The sensor controller 32 calculates the rotation angle α of the boom 6in relation to the vertical direction of the vehicle body 1 from theboom cylinder length acquired based on the detection result of the firststroke sensor 16. The sensor controller 32 calculates the rotation angleβ of the arm 7 in relation to the boom 6 from the arm cylinder lengthacquired based on the detection result of the second stroke sensor 17.The sensor controller 32 calculates the rotation angle γ of the cuttingedge 8 a of the bucket 8 in relation to the arm 7 from the bucketcylinder length acquired based on the detection result of the thirdstroke sensor 18.

The rotation angle α of the boom 6, the rotation angle β of the arm 7,and the rotation angle γ of the bucket 8 may not be detected by thestroke sensor. The rotation angle α of the boom 6 may be detected by anangle detector such as a rotary encoder. The angle detector detects abending angle of the boom 6 with respect to the revolving structure 3 todetect the rotation angle α. Similarly, the rotation angle β of the arm7 may be detected by an angle detector attached to the arm 7. Therotation angle γ of the bucket 8 may be detected by an angle detectorattached to the bucket 8.

The sensor controller 32 acquires the cylinder length data L and thework machine angle data from the first, second, and third stroke sensors16, 17, and 18. The sensor controller 32 outputs the work machinerotation angle data α to γ to the display controller 28 and the workmachine controller 26.

The display controller 28 acquires the vehicle body position data P andthe vehicle body attitude data Q from the position detection device 20.Moreover, the display controller 28 acquires the tilt angle dataindicating the tilt angle δ from the tilt angle sensor 70.

The display controller 28 acquires the vehicle body position data P andthe vehicle body attitude data Q from the position detection device 20.Moreover, the display controller 28 acquires the tilt angle dataindicating the tilt angle δ from the tilt angle sensor 70.

The display controller 28 includes a calculation unit 280A that performsa calculating process, a storage unit 280B in which data is stored, andan acquisition unit (data acquisition unit) 280C that acquires data.

The display controller 28 calculates target excavation landform data Ubased on stored target construction information, work machinedimensions, the vehicle body position data P, the vehicle body attitudedata Q, and the rotation angle data α to γ of the respective workmachines and outputs the target excavation landform data U to the workmachine controller 26.

The work machine controller 26 includes a work machine control unit 26A,a driving inhibiting unit 26B, and a storage unit 26C. The work machinecontroller 26 receives the target excavation landform data U from thedisplay controller 28 and acquires the rotation angle data α to γ of therespective work machines from the sensor controller 32. The work machinecontroller 26 generates a control command to the control valve 27 basedon the target excavation landform data U and the rotation angle data αto γ of the work machines. Moreover, the work machine controller 26outputs an operation command for operating a tilt bucket to the pumpcontroller 34.

The pump controller 34 outputs a driving command to the hydraulic pump41 that supplies operating oil to the work machine 2. Moreover, the pumpcontroller 34 outputs a command to control valves 27D and 27E (describedlater) in order to control the tilt angle of the bucket 8.

[Stroke Sensor]

Next, the stroke sensor 16 will be described with reference to FIGS. 10and 11. In the following description, the stroke sensor 16 attached tothe boom cylinder 10 will be described. The stroke sensor 17 and thelike attached to the arm cylinder 11 have the same configuration as thestroke sensor 16.

The stroke sensor 16 is attached to the boom cylinder 10. The strokesensor 16 measures the stroke of a piston. As illustrated in FIG. 10,the boom cylinder 10 includes a cylinder tube 10X and a cylinder rod 10Yconfigured to move within the cylinder tube 10X in relation to thecylinder tube 10X. A piston 10V is slidably provided in the cylindertube 10X. The cylinder rod 10Y is attached to the piston 10V. Thecylinder rod 10Y is slidably provided in a cylinder head 10W. A chamberformed by the cylinder head 10W, the piston 10V, and a cylinder innerwall is a rod-side oil chamber 40B. An oil chamber on the opposite sideof the rod-side oil chamber 40B with the piston 10V interposed is acap-side oil chamber 40A. A seal member is provided in the cylinder head10W so as to seal the gap between the cylinder head 10W and the cylinderrod 10Y so that dust or the like does not enter into the rod-side oilchamber 40B.

The cylinder rod 10Y retracts when operating oil is supplied to therod-side oil chamber 40B and the operating oil is discharged from thecap-side oil chamber 40A. Moreover, the cylinder rod 10Y extends whenoperating oil is discharged from the rod-side oil chamber 40B and theoperating oil is supplied to the cap-side oil chamber 40A. That is, thecylinder rod 10Y moves linearly in the left-right direction in thefigure.

A case 164 that covers the stroke sensor 16 and accommodates the strokesensor 16 is provided outside the rod-side oil chamber 40B at theproximity of the cylinder head 10W. The case 164 is fixed to thecylinder head 10W by being fastened to the cylinder head 10W by bolts orthe like.

The stroke sensor 16 includes a rotation roller 161, a rotation centershaft 162, and a rotation sensor portion 163. The rotation roller 161has a surface in contact with the surface of the cylinder rod 10Y and isprovided so as to rotate according to linear movement of the cylinderrod 10Y. That is, linear movement of the cylinder rod 10Y is convertedinto rotational movement by the rotation roller 161. The rotation centershaft 162 is disposed to be orthogonal to the direction of linearmovement of the cylinder rod 10Y.

The rotation sensor portion 163 is configured to detect the amount ofrotation (rotation angle) of the rotation roller 161 as an electricalsignal. The signal indicating the amount of rotation (rotation angle) ofthe rotation roller 161 detected by the rotation sensor portion 163 isoutput to the sensor controller 32 via an electrical signal line and isconverted to the position (stroke position) of the cylinder rod 10Y ofthe boom cylinder 10 by the work machine controller 26.

As illustrated in FIG. 11, the rotation sensor portion 163 includes amagnet 163 a and a hall IC 163 b. The magnet 163 a which is a detectingmedium is attached to the rotation roller 161 so as to rotate integrallywith the rotation roller 161. The magnet 163 a rotates with rotation ofthe rotation roller 161 around the rotation center shaft 162. The magnet163 a is configured such that the N pole and the S pole alternateaccording to the rotation angle of the rotation roller 161. The magnet163 a is configured such that magnetic force (magnetic flux density)detected by the hall IC 163 b changes periodically every rotation of therotation roller 161.

The hall IC 163 b is a magnetic force sensor that detects the magneticforce (magnetic flux density) generated by the magnet 163 a as anelectrical signal. The hall IC 163 b is provided along the axialdirection of the rotation center shaft 162 at a position separated by apredetermined distance from the magnet 163 a.

The electrical signal detected by the hall IC 163 b is output to thework machine controller 26, and the electrical signal of the hall IC 163b is converted to the amount of rotation of the rotation roller 161(that is, the displacement amount (stroke length) of the cylinder rod10Y of the boom cylinder 10) by the work machine controller 26.

Here, referring to FIG. 11, a relation between the rotation angle of therotation roller 161 and the electrical signal (voltage) detected by thehall IC 163 b will be described. When the rotation roller 161 rotatesand the magnet 163 a rotates with the rotation, the magnetic force(magnetic flux density) that passes through the hall IC 163 b changesperiodically according to the rotation angle and the electrical signal(voltage) which is the sensor output changes periodically. The rotationangle of the rotation roller 161 can be measured from the magnitude ofthe voltage output from the hall IC 163 b.

Moreover, by counting the number of repetitions of each cycle of theelectrical signal (voltage) output from the hall IC 163 b, it ispossible to measure the number of rotations of the rotation roller 161.Moreover, the displacement amount (stroke length) of the cylinder rod10Y of the boom cylinder 10 is detected based on the rotation angle ofthe rotation roller 161 and the number of rotations of the rotationroller 161.

Moreover, the stroke sensor 16 can detect the moving speed (cylinderspeed) of the cylinder rod 10Y based on the rotation angle of therotation roller 161 and the number of rotations of the rotation roller161.

[Hydraulic System]

Next, an example of a hydraulic system 300 according to the presentembodiment will be described. The control system 200 includes thehydraulic system 300 and the work machine controller 26. The boomcylinder 10, the arm cylinder 11, the bucket cylinder 12, and the tiltcylinder 30 are hydraulic cylinders. These hydraulic cylinders areoperated by the hydraulic system 300.

FIG. 13 is a diagram schematically illustrating an example of thehydraulic system 300 including the arm cylinder 11. The same is true forthe bucket cylinder 12. The hydraulic system 300 includes a variablecapacitance main hydraulic pump 41 that supplies operating oil to thearm cylinder 11 via the direction control valve 64, a pilot hydraulicpump 42 that supplies pilot oil, the operating device 25 that adjuststhe pilot pressure of the pilot oil to the direction control valve 64,an oil passage 43 (43A and 43B) through which the pilot oil flows, thecontrol valve 27 (27A and 27B) disposed in the oil passage 43, thepressure sensor 66 (66A and 66B) disposed in the oil passage 43, and thework machine controller 26 that controls the control valve 27. The oilpassage 43 is the same as the pilot pressure line 450 of FIG. 9.

The direction control valve 64 controls the direction in which operatingoil flows. The operating oil supplied from the main hydraulic pump 41 issupplied to the arm cylinder 11 via the direction control valve 64. Thedirection control valve 64 is a spool-type valve in which a rod-shapedspool is moved to change the flowing direction of operating oil. Whenthe spool moves in an axial direction, the supply of operating oil tothe cap-side oil chamber 40A (an oil passage 47) of the arm cylinder 11and the supply of operating oil to the rod-side oil chamber 40B (an oilpassage 48) are switched. Moreover, when the spool moves in the axialdirection, the amount (the amount of supply per unit time) of operatingoil supplied to the arm cylinder 11 is adjusted. When the amount ofoperating oil supplied to the arm cylinder 11 is adjusted, the cylinderspeed is adjusted.

The driving of the direction control valve 64 is adjusted by theoperating device 25. In the present embodiment, the operating device 25is a pilot hydraulic-type operating device. Pilot oil which has beendelivered from the pilot hydraulic pump 42 is supplied to the operatingdevice 25. Pilot oil which has been delivered from the main hydraulicpump 41 and decompressed by the pressure-reducing valve may be suppliedto the operating device 25. The operating device 25 includes a pilotpressure adjustment valve. The pilot pressure is adjusted based on theamount of operation of the operating device 25. The direction controlvalve 64 is driven with the pilot pressure. When the pilot pressure isadjusted by the operating device 25, the movement amount and the movingspeed of the spool in the axial direction are adjusted.

Two oil passages 43 through which pilot oil flows are provided in eachdirection control valve 64. Pilot oil supplied to one space (firstpressure receiving chamber) of a spool of the direction control valve 64flows through one oil passage 43A of the two oil passages 43A and 43B.Pilot oil supplied to the other space (second pressure receivingchamber) of the spool of the direction control valve 64 flows throughthe other oil passage 43B.

The pressure sensor 66 is disposed in the oil passage 43. The pressuresensor 66 detects the pilot pressure. The pressure sensor 66 includesthe pressure sensor 66A that detects the pilot pressure of the oilpassage 43A and the pressure sensor 66B that detects the pilot pressureof the oil passage 43B. The detection result of the pressure sensor 66is output to the work machine controller 26.

The control valve 27 is an electromagnetic proportional control valveand can adjust the pilot pressure based on the control signal from thework machine controller 26. The control valve 27 includes a controlvalve 27A that can adjust the pilot pressure of the oil passage 43A anda control valve 27B that can adjust the pilot pressure of the oilpassage 43B.

When the pilot pressure is adjusted by the operation of the operatingdevice 25, the control valve 27 is open to its full width. When theoperating lever of the operating device 25 is operated to one side fromthe neutral position, pilot pressure corresponding to the amount ofoperation of the operating lever acts on the first pressure receivingchamber of the spool of the direction control valve 64. When theoperating lever of the operating device 25 is operated to the other sidefrom the neutral position, pilot pressure corresponding to the amount ofoperation of the operating lever acts on the second pressure receivingchamber of the spool of the direction control valve 64.

The spool of the direction control valve 64 is moved by the distancecorresponding to the pilot pressure adjusted by the operating device 25.For example, when the pilot pressure acts on the first pressurereceiving chamber, the operating oil from the main hydraulic pump 41 issupplied to the cap-side oil chamber 40A of the arm cylinder 11 and thearm cylinder 11 is extended. When the pilot pressure acts on the secondpressure receiving chamber, the operating oil from the main hydraulicpump 41 is supplied to the rod-side oil chamber 40B of the arm cylinder11 and the arm cylinder 11 is retracted. Based on the movement amount ofthe spool of the direction control valve 64, the amount of operating oilsupplied per unit time from the main hydraulic pump 41 to the armcylinder 11 via the direction control valve 64 is adjusted. When theamount of operating oil supplied per unit time is adjusted, the cylinderspeed is adjusted.

The work machine controller 26 can control the control valve 27 toadjust the pilot pressure. For example, in limited excavation control(intervention control), the work machine controller 26 drives thecontrol valve 27. For example, when the control valve 27A is driven bythe work machine controller 26, the spool of the direction control valve64 is moved by the distance corresponding to the pilot pressure adjustedby the control valve 27A. In this way, the operating oil from the mainhydraulic pump 41 is supplied to the cap-side oil chamber 40A of the armcylinder 11 and the arm cylinder 11 is extended. When the control valve27B is driven by the work machine controller 26, the spool of thedirection control valve 64 is moved by the distance corresponding to thepilot pressure adjusted by the control valve 27B. In this way, theoperating oil from the main hydraulic pump 41 is supplied to therod-side oil chamber 40B of the arm cylinder 11 and the arm cylinder 11is retracted. Based on the movement amount of the spool of the directioncontrol valve 64, the amount of operating oil supplied per unit timefrom the main hydraulic pump 41 to the arm cylinder 11 via the directioncontrol valve 64 is adjusted. When the amount of operating oil suppliedper unit time is adjusted, the cylinder speed is adjusted.

FIG. 14 is a diagram schematically illustrating an example of thehydraulic system 300 including the boom cylinder 10. According to theoperation of the operating device 25, the boom 6 executes two operationsof the lowering operation and the raising operation. As described abovewith reference to FIG. 13, when the operating device 25 is operated, thepilot pressure corresponding to the amount of operation of the operatingdevice 25 acts on the direction control valve 64. The spool of thedirection control valve 64 is moved based on the pilot pressure. Basedon the movement amount of the spool, the amount of operating oilsupplied per unit time from the main hydraulic pump 41 to the boomcylinder 10 via the direction control valve 64 is adjusted.

Moreover, the work machine controller 26 can drive the control valve 27Ato adjust the pilot pressure acting on the second pressure receivingchamber. The work machine controller 26 can drive the control valve 27Bto adjust the pilot pressure acting on the first pressure receivingchamber. In the example illustrated in FIG. 14, when the pilot oil issupplied to the direction control valve 64 via the control valve 27A,the lowering operation of the boom 6 is executed. When the pilot oil issupplied to the direction control valve 64 via the control valve 27B,the raising operation of the boom 6 is executed.

In the present embodiment, an oil passage 43C is connected to a controlvalve 27C that operates based on an intervention control signal outputfrom the work machine controller 26 in order to perform interventioncontrol. The pilot oil delivered from the pilot hydraulic pump 42 flowsthrough the oil passage 43C. The oil passage 43C is connected to the oilpassage 43B with a shuttle valve 51 interposed. The shuttle valve 51selects the input from an oil passage having the larger pressure amongthe oil passages connected thereto and outputs the same.

The control valve 27C and a pressure sensor 66C that detects the pilotpressure of the oil passage 43C are provided in the oil passage 43C. Thecontrol valve 27C is controlled based on a control signal output fromthe work machine controller 26 in order to execute intervention control.

When intervention control is not executed, the work machine controller26 does not output a control signal to the control valve 27C so that thedirection control valve 64 is driven based on the pilot pressureadjusted by the operation of the operating device 25. For example, thework machine controller 26 opens the control valve 27B to its full widthand closes the control valve 27C and the oil passage 43C so that thedirection control valve 64 is driven based on the pilot pressureadjusted by the operation of the operating device 25.

When intervention control is executed, the work machine controller 26controls the respective control valves 27 so that the direction controlvalve 64 is driven based on the pilot pressure adjusted by the controlvalve 27C. For example, when intervention control of limiting themovement of the boom 6 is executed, the work machine controller 26controls the control valve 27C so that the pilot pressure adjusted bythe control valve 27C is higher than the pilot pressure adjusted by theoperating device 25. The pilot pressure supplied from the oil passage43C becomes larger than the pilot pressure supplied from the oil passage43B. In this way, the pilot oil from the control valve 27C is suppliedto the direction control valve 64 via the shuttle valve 51.

When the pilot oil is supplied to the direction control valve 64 via atleast one of the oil passages 43B and 43C, the operating oil is suppliedto the cap-side oil chamber 40A through the oil passage 47. In this way,the boom 6 is raised.

When the boom 6 is raised at a high speed by the operating device 25 sothat the bucket 8 does not dig into the target excavation landform, theintervention control is not executed. When the operating device 25 isoperated so that the boom 6 is raised at a high speed and the pilotpressure is adjusted based on the amount of operation, the pilotpressure adjusted by the operation of the operating device 25 becomeshigher than the pilot pressure adjusted by the control valve 27C. Inthis way, the pilot oil having the pilot pressure adjusted by theoperation of the operating device 25 is supplied to the directioncontrol valve 64 via the shuttle valve 51.

FIG. 15 is a diagram schematically illustrating an example of thehydraulic system 300 including the tilt cylinder 30. The hydraulicsystem 300 includes the direction control valve 64 that adjusts theamount of operating oil supplied to the tilt cylinder 30, the controlvalve 27D and the control valve 27D that adjust the pressure of thepilot oil supplied to the direction control valve 64, an operation pedal25F, and the pump controller 34. The pump controller 34 outputs acommand signal to a swash plate of the main hydraulic pump 41 andcontrols the amount of operating oil supplied to the hydraulic cylinder.The control valve 27 is controlled based on a control signal generatedby the pump controller 34 based on an operation signal of the operatingdevice 25 (the third operating lever 25P).

In the present embodiment, the operation signal generated by theoperation of the third operating lever 25P is output to the pumpcontroller 34. The operation signal generated by the operation of thethird operating lever 25P may be output to the work machine controller26. The control valve 27 may be controlled by the pump controller 34 andmay be controlled by the work machine controller 26.

In the present embodiment, the operating device 25 includes theoperation pedal 25F for adjusting the pilot pressure to the directioncontrol valve 64. The operation pedal 25F is disposed in the cab 4 andis operated by the operator. The operation pedal 25F is connected to thepilot hydraulic pump 42. Moreover, the operation pedal 25F is connectedto an oil passage through which the pilot oil delivered from the controlvalve 27D flows with a shuttle valve 51A interposed. Moreover, theoperation pedal 25F is connected to an oil passage through which thepilot oil delivered from the control valve 27E flows with a shuttlevalve 51B interposed.

When the operation pedal 25F is operated, the pressure of the oilpassage between the operation pedal 25F and the shuttle valve 51A andthe pressure of the oil passage between the operation pedal 25F and theshuttle valve 51B are adjusted.

When the third operating lever 25P is operated, an operation signal(command signal) based on the operation of the third operating lever 25Pis output to the pump controller 34 (or the work machine controller 26).The pump controller 34 outputs a control signal to at least one of thecontrol valve 27D and the control valve 27E based on the operationsignal output from the third operating lever 25P. The control valve 27Dhaving acquired the control signal is driven in such a manner to openand close the oil passage. The control valve 27B having acquired thecontrol signal is driven in such a manner to open and close the oilpassage.

According to the operation of at least one of the operation pedal 25Fand the third operating lever 25P, when the pilot pressure adjusted bythe control valve 27D is higher than the pilot pressure adjusted by theoperation pedal 25F, the pilot oil having the pilot pressure, selectedby the shuttle valve 51A and adjusted by the control valve 27D issupplied to the direction control valve 64. When the pilot pressureadjusted by the operation pedal 25F is higher than the pilot pressureadjusted by the control valve 27D, the pilot oil having the pilotpressure adjusted by the operation pedal 25F is supplied to thedirection control valve 64.

According to the operation of at least one of the operation pedal 25Fand the third operating lever 25P, when the pilot pressure adjusted bythe control valve 27E is higher than the pilot pressure adjusted by theoperation pedal 25F, the pilot oil having the pilot pressure, selectedby the shuttle valve 51B and adjusted by the control valve 27E issupplied to the direction control valve 64. When the pilot pressureadjusted by the operation pedal 25F is higher than the pilot pressureadjusted by the control valve 27E, the pilot oil having the pilotpressure adjusted by the operation pedal 25F is supplied to thedirection control valve 64.

[Limited Excavation Control]

FIG. 12 is a diagram schematically illustrating an example of theoperation of the work machine 2 when limited excavation control isperformed. In the present embodiment, limited excavation control isperformed so that the bucket 8 does not dig into a target excavationlandform indicating a 2-dimensional target shape of an excavation objectin a working plane MP orthogonal to the bucket shaft J3.

When the bucket 8 performs excavation, the hydraulic system 300 operatesso that the boom 6 is raised in relation to the excavation operation ofthe arm 7 and the bucket 8. During the excavation, intervention controlincluding the raising operation of the boom 6 is executed so that thebucket 8 does not dig into the target excavation landform.

[Control Method]

Next, an example of a method of controlling the excavator CM accordingto the present embodiment will be described with reference to theflowchart of FIG. 16. The display controller 28 acquires variousparameters used for excavation control (step SP1). The parameters areacquired by an acquisition unit 28C of the display controller 28.

FIG. 17A is a functional block diagram illustrating an example of thedisplay controller 28, the work machine controller 26, and the sensorcontroller 32 according to the present embodiment. The sensor controller32 includes a calculation unit 28A, a storage unit 28B, and theacquisition unit 28C. The calculation unit 28A includes a work machineangle calculation unit 281A, a tilt angle data calculation unit 282A,and a 2-dimensional bucket data calculation unit 283A. The acquisitionunit 28C includes a work machine data acquisition unit 281C, a bucketshape data acquisition unit 282C, a work machine angle acquisition unit284C, and a tilt angle acquisition unit 285C.

FIG. 17B is a functional block diagram illustrating an example of thework machine control unit 26A of the work machine controller 26according to the present embodiment. As illustrated in FIG. 17B, thework machine control unit 26A of the work machine controller 26 includesa relative position calculation unit 260A, a distance calculation unit260B, a target speed calculation unit 260C, an intervention speedcalculation unit 260D, an intervention command calculation unit 260E.The work machine control unit 26A limits the speed of the boom 6 basedon the target excavation landform data U indicating the targetexcavation landform which is a target shape of an excavation object andthe bucket position data indicating the position of the bucket 8 (thecutting edge 8 a) so that a relative speed at which the bucket 8approaches the target excavation landform decreases according to thedistance d between the target excavation landform and the bucket 8 (thecutting edge 8 a). The work machine controller 26 performs calculationin the local coordinate system.

As illustrated in FIG. 17A, the display controller 283C includes atarget excavation landform acquisition unit 283C and a target excavationlandform calculation unit 284A.

The acquisition unit 28C includes the work machine data acquisition unit(first acquisition unit) 281C, the bucket shape data acquisition unit(fourth acquisition unit) 282C, the work machine angle acquisition unit(third acquisition unit) 284C that acquires work machine angle data, andthe tilt angle acquisition unit (fifth acquisition unit) 285C thatacquires tilt angle data. The target excavation landform acquisitionunit (third acquisition unit) 283C is included in the display controller28.

The calculation unit 28A includes the work machine angle calculationunit 281A that calculates a work machine angle and the 2-dimensionalbucket data calculation unit 283A that calculate 2-dimensional bucketdata. The relative position calculation unit 260A that calculates therelative position of the bucket 8 in relation to the target excavationlandform is included in the work machine controller 26 (the work machinecontrol unit 26A). The target excavation landform calculation unit 284Ais included in the display controller 28.

The work machine controller 26 outputs a control signal for controllingthe work machine 2. The work machine controller 26 includes the workmachine control unit 26A that outputs a control signal. As illustratedin FIG. 9, in the present embodiment, the work machine controller 26includes a driving inhibiting unit 26B that inhibits driving of thebucket 8. The driving inhibiting unit 26B inhibits rotation (tilting) ofthe bucket 8 about the tilt shaft J4. The driving inhibiting unit 26Bmay inhibit rotation (vertical movement) of the bucket 8 about thebucket shaft J3. In the present embodiment, the driving inhibiting unit26B stops the driving (tilting) of the bucket 8 by disabling theoperation signal output from the operating device 25 in order to operatethe tilt cylinder 30 that tilts the bucket 8.

The work machine angle calculation unit 281A acquires the boom cylinderlength from the first stroke sensor 16 to calculate a boom angle α. Thework machine angle calculation unit 281A acquires the arm cylinderlength from the second stroke sensor 17 to calculate an arm angle β. Thework machine angle calculation unit 281A acquires the bucket cylinderlength from the third stroke sensor 18 to calculate a bucket angle γ.The work machine angle acquisition unit 284C acquires work machine angledata including the boom angle data, the arm angle data, and the bucketangle data (step SP1.2).

The boom angle α, the arm angle β, and the bucket angle γ may not bedetected by the stroke sensor. The boom angle α may be detected by aninclination angle sensor attached to the boom 6. The arm angle β may bedetected by an inclination sensor attached to the arm 7. The bucketangle γ may be detected by an inclination angle sensor attached to thebucket 8. When the angle detection device 22 includes an inclinationangle sensor, the work machine angle data acquired by the angledetection device 22 is output to the sensor controller 32.

The acquisition unit 28C (the work machine angle acquisition unit 284C)of the sensor controller 32 acquires work machine angle data includingthe boom angle data indicating the boom angle α, the arm angle dataindicating the arm angle β, and the bucket angle data indicating thebucket angle γ based on the detection result of the angle detectiondevice 22. Moreover, the acquisition unit 28C (the tilt angleacquisition unit 285C) acquires tilt angle data including a tilt angleδ′ indicating the rotation angle of the bucket about the tilt shaftbased on the detection result of the tilt angle sensor 70. Moreover, theacquisition unit 28C (the tilt angle acquisition unit 285C) acquirestilt shaft angle data including a tilt shaft angle ε′ indicating therotation angle of the bucket about the tilt shaft based on the detectionresult of the angle detection device 22. During the driving of the workmachine 2, the angle detection device 22 and the tilt angle sensor 70monitors the boom angle α, the arm angle β, the bucket angle γ, the tiltangle δ, and the tilt shaft angle ε. The acquisition unit 28C acquiresthese items of angle data in realtime during the driving of the workmachine 2.

The tilt angle sensor 70 detects tilt angle data indicating the tiltangle δ of the bucket 8 about the tilt shaft J4. The tilt angle dataacquired by the tilt angle sensor 70 is output to the sensor controller32 via the display controller 28. The tilt angle acquisition unit 285Cacquires the tilt angle data indicating the rotation angle of the bucketabout the tilt shaft (step SP1.4).

In the present embodiment, the tilt angle data is output from the tiltangle sensor 70 to the acquisition unit 28C (the tilt angle acquisitionunit 285C). A fixing unit 28D fixes the tilt angle data (monitor data)output from the tilt angle sensor 70 to the acquisition unit 28C basedon a fixing command to generate fixed data.

When the bucket 8 rotates about the bucket shaft J3, the tilt pin 80(the tilt shaft J4) is also rotated (inclined) in the θY direction. Thetilt angle acquisition unit 285C acquires the tilt shaft angle dataindicating the inclination angle ε of the tilt shaft J4 in relation tothe XY plane based on the detection result of the angle detection device22.

The storage unit 28B of the sensor controller 32 stores work machinedata. The work machine data includes dimension data of the work machine2 and the shape data of the bucket 8.

The dimension data of the work machine 2 includes the dimension data ofthe boom 6, the dimension data of the arm 7, and the dimension data ofthe bucket 8. The dimension data of the work machine 2 includes a boomlength L1, an arm length L2, a bucket length L3, and a tilt length L4.The boom length L1, the arm length L2, the bucket length L3, and thetilt length L4 are dimensions in the XZ plane (the vertical rotationplane).

The work machine data acquisition unit 281C acquires the dimension dataof the work machine 2, including the dimension data of the boom 6, thedimension data of the arm 7, and the dimension data of the bucket 8,from the storage unit 28B.

The shape data of the bucket 8 includes outline data of the outersurface of the bucket 8. The shape data of the bucket 8 is data forspecifying the dimensions and the shape of the bucket 8. The shape dataof the bucket 8 includes distal end position data indicating theposition of the distal end 8 a of the bucket 8. The shape data of thebucket 8 includes coordinate data of a plurality of positions of theouter surface of the bucket 8 based on the distal end 8 a, for example.

The shape data of the bucket 8 includes a dimension L5 of the bucket 8in relation to the width direction of the bucket 8. When the bucket 8 isnot tilted, the width dimension L5 of the bucket 8 is the dimension ofthe bucket 8 in the Y-axis direction of the local coordinate system.When the bucket 8 is tilted, the width dimension L5 of the bucket 8 isdifferent from the dimension of the bucket 8 in relation to the Y-axisdirection of the local coordinate system.

The bucket shape data acquisition unit 282C acquires the shape data ofthe bucket 8 from the storage unit 28B.

In the present embodiment, both the work machine dimension dataincluding the boom length L1, the arm length L2, the bucket length L3,the tilt length L4, and the bucket width L5 and the bucket shape dataincluding the shape data of the bucket 8 are stored in the storage unit28B.

The work machine angle calculation unit 281A calculates work machineangle data indicating the rotation angles of the respective workmachines from the respective cylinder strokes of the boom 6, the arm 7,and the bucket 8.

The tilt angle calculation unit 282A acquires the tilt shaft angle ε′and the tilt angle δ′ which is the tilt angle data indicating therotation angle of the bucket about the tilt shaft from the tilt angle δ,the tilt shaft angle ε, and the inclination angles θ1 and θ2.

The data fixed by the fixing unit 28D is the tilt angle data calculatedby the tilt angle data calculation unit 282A.

The 2-dimensional bucket data calculation unit 283A generates2-dimensional bucket data S indicating the outer shape of the bucket 8in a working plane MP described later and the cutting edge position Paof the cutting edge 8 a of the bucket 8 based on the work machine angledata, the work machine dimension data, the bucket shape data, the Ycoordinate of a cross-section represented by the Y coordinate of theworking plane MP, and the tilt angle data indicating the rotation angleof the bucket about the tilt shaft.

The target excavation landform acquisition unit 283C acquires targetconstruction information T indicating a 3-dimensional designed landformwhich is a 3-dimensional target shape of an excavation object andacquires the vehicle body position data P and the vehicle body attitudedata Q from the position detection device 20. The target excavationlandform calculation unit 284A generates target excavation landform dataU indicating the target excavation landform which is a 2-dimensionaltarget shape of an excavation object in the working plane MP orthogonalto the bucket shaft J3 from the data acquired from the target excavationlandform acquisition unit 283C, the inclination angles θ1 and θ2acquired from the 2-dimensional bucket data calculation unit 283A, the2-dimensional bucket data S indicating the outer shape of the bucket 8,and the cutting edge 8 a of the bucket 8.

The relative position calculation unit 260A calculates a relativeposition on the bucket 8 at which the distance on an outline point Ni(described later) of the bucket 8 to the target excavation landform isthe shortest based on the rotation angle data α to γ of the respectivework machines input from the sensor controller 32, the 2-dimensionalbucket data S, and the target excavation landform data U input from thedisplay controller 28 and outputs the relative position to the distancecalculation unit 260B. The distance calculation unit 260B calculates theshortest distance d between the target excavation landform and thebucket 8 based on the relative position of the bucket 8 and the targetexcavation landform.

The target speed calculation unit 260C receives the pressure of thepilot pressure sensors 66A and 66B based on the lever operations ofrespective work machine levers (described later). The target speedcalculation unit 260C derives target speeds Vc_bm, Vc_am, and Vc_bk ofthe respective work machines using a table that defines the relation ofthe target speeds of the respective work machines with respect to thepressure stored in the storage unit 27C by the pressure sensors 66A and66B and outputs the target speeds to the intervention speed calculationunit 260D.

The intervention speed calculation unit 260D calculates a speed limitcorresponding to the distance d between the relative position of thebucket 8 and the target excavation landform based on the target speedsof the respective work machines, the distance d between the targetexcavation landform data U and the bucket 8. The speed limit is outputto the intervention command calculation unit 260E as an interventionspeed of the boom work machine.

The intervention command calculation unit 260E determines anintervention command corresponding to the speed limit for extending theboom cylinder 10. The intervention command calculation unit 260E outputsthe intervention command so as to open the control valve 27C so that thepilot pressure is generated in the control valve 27C. The boom 6 isdriven according to the command from the work machine controller 28 sothat the speed in the direction in which the work machine 2 approachesthe target excavation landform is the speed limit. In this way, thelimited excavation control on the cutting edge 8 a is executed, and thespeed of the bucket 8 in relation to the target excavation landform isadjusted.

Moreover, the display controller 28 displays the target excavationlandform on the display unit 29 based on the target excavation landformdata U. Moreover, the display controller 28 displays the targetexcavation landform data U and the 2-dimensional bucket data S on thedisplay unit 29. The display unit 29 is a monitor, for example, anddisplays various types of information on the excavator CM. In thepresent embodiment, the display unit 29 includes a human machineinterface (HMI) monitor as a guidance monitor for information-orientedconstruction.

The display controller 28 can calculate the local coordinate positionwhen seen in the global coordinate system based on the detection resultof the position detection device 20. The local coordinate system is a3-dimensional coordinate system based on an excavator 100. In thepresent embodiment, the reference position P0 of the local coordinatesystem is the reference position P0 positioned at the revolution centerAX of the revolving structure 3, for example. For example, although thetarget excavation landform data output to the work machine controller 26is converted into a local coordinate, calculations in the displaycontroller 28 are performed in the global coordinate system. The inputfrom the sensor controller 32 is also converted into a global coordinatesystem in the display controller 28.

During the driving of the work machine 2, the boom angle α, the armangle β, and the bucket angle γ are detected by the angle detectiondevice 22. The tilt angle δ is detected by the tilt angle sensor 70.Moreover, the tilt shaft angle ε is detected by the angle detectiondevice 22.

Moreover, the acquisition unit 28C acquires the dimension data of thework machine 2, including the boom length L1, the arm length L2, thebucket length L3, the tilt length L4, and the width dimension L5 of thebucket 8, from the work machine data stored in the storage unit 28B. Thework machine data including the dimension data of the work machine 2 maybe supplied to the acquisition unit 28C (the work machine dataacquisition unit 281C) via the input unit 36.

Moreover, the acquisition unit 28C (the bucket shape data acquisitionunit 282C) acquires the shape data of the bucket 8. The shape data ofthe bucket 8 may be stored in the storage unit 28B, and may be acquiredby the acquisition unit 28C (the bucket shape data acquisition unit282C) via the input unit 36.

Moreover, the acquisition unit 28C acquires the vehicle body positiondata P and the vehicle body attitude data Q based on the positiondetection result of the position detection device 20. The acquisitionunit 28C acquires these items of data in realtime during the driving ofthe excavator CM.

Moreover, the acquisition unit 28C (the target excavation landformacquisition unit 283C) acquires target construction information(3-dimensional designed landform data) T indicating a 3-dimensionaldesigned landform which is a 3-dimensional target shape of an excavationobject of a work area. The target construction information T includestarget excavation landform data (2-dimensional designed landform data) Uindicating a target excavation landform which is a 2-dimensional targetshape of an excavation object. In the present embodiment, the targetconstruction information T is stored in the storage unit 28B of thedisplay controller 28. The target construction information T includescoordinate data and angle data required for generating the targetexcavation landform data U. The target construction information T may besupplied to the display controller 28 via a radio communication device,for example and may be supplied to the display controller 28 via anexternal memory or the like.

As described above, in the present embodiment, the tilt angle sensor 70detects the tilt angle in the global coordinate system. In the displaycontroller 28, the tilt angle in the global coordinate system isconverted into the tilt angle δ in the local coordinate system based onthe vehicle body attitude data Q. The tilt angle δ may be calculated bycalculating the attitude information of the IMU and the retractioninformation of the tilt cylinder 30 according to the same method as therespective work machines and calculating the inclination angle.

Subsequently, in the present embodiment, the target excavation landformdata U indicating the target excavation landform which is a2-dimensional target shape of an excavation object in the working planeMP orthogonal to the bucket shaft J3 is designated (step SP2). Thedesignation of the target excavation landform data U includesdesignating a cross-section of the target construction information Tparallel to the XZ plane. The designation of the target excavationlandform data U includes designating the position (Y coordinate) in theY-axis direction at which the target construction information T is cutalong a cross-section. The target construction information T on thecross-section parallel to the XZ plane having the Y coordinate is thedesignated target excavation landform data U.

As illustrated in FIG. 18, the target construction information T isrepresented by a plurality of triangular polygons. In the targetconstruction information T, the working plane MP orthogonal to thebucket shaft J3 is designated. The working plane MP is a working plane(vertical rotation plane) of the work machine 2 defined in thefront-rear direction of the revolving structure 3. In the presentembodiment, the working plane MP is the working plane of the arm 6. Theworking plane MP is parallel to the XZ plane.

The position (the Y coordinate of the working plane MP) of the cuttingedge 8 a of the bucket 8 may be designated by an operator. For example,the operator may input data on the Y coordinate designated by the inputunit 36. The designated Y coordinate is acquired by the acquisition unit28C. The acquisition unit 28C calculates the cross-section of the targetconstruction information T in the working plane MP having the Ycoordinate. In this way, the target excavation landform calculation unit283C acquires the target excavation landform data U of the designated Ycoordinate.

The Y coordinate of a point on the surface of the target constructioninformation at which the distance to the bucket 8 is the shortest may bedesignated as the Y coordinate of the working plane MP.

For example, the display controller 28 acquires a nodal line E betweenthe working plane MP and the target construction information as acandidate line of the target excavation landform based on the targetconstruction information T and the designated working plane MP asillustrated in FIG. 18.

The display controller 28 sets a point of the candidate line of thetarget excavation landform located immediately below the cutting edge 8a as a reference point AP of the target excavation landform. The displaycontroller 28 determines a single or a plurality of inflection pointsappearing before and after the reference point AP of the targetexcavation landform and lines appearing before and after the inflectionpoints as the target excavation landform which serves as an excavationobject. The display controller 28 generates the target excavationlandform data U in the working plane MP.

Subsequently, the calculation unit 28A (the 2-dimensional bucket datacalculation unit 283A) of the sensor controller 32 calculates the2-dimensional bucket data S indicating the outer shape of the bucket 8in the working plane MP based on the parameters (data) acquired in stepSP1 (step SP3).

FIG. 19 is a rear view schematically illustrating an example of thebucket 8 in a tilted state. FIG. 20 is a side sectional view taken alongthe line A-A in FIG. 19. FIG. 21 is a side sectional view taken alongthe line B-B in FIG. 19. FIG. 22 is a side sectional view taken alongthe line C-C in FIG. 19.

In the present embodiment, since the bucket 8 is tilted, the outer shape(outline) of the bucket 8 in the XZ plane changes according to the tiltangle δ. Moreover, as illustrated in FIGS. 20, 21, and 22, when the Ycoordinates of the cross-sections parallel to the XZ plane aredifferent, the outer shapes (outlines) of the bucket 8 in the respectivecross-sections are different. Moreover, when the bucket 8 is tilted, thedistance between the target excavation landform and the bucket 8changes.

In a bucket (a so-called standard bucket) having no tilting mechanism,even when the Y coordinate of the cross-section parallel to the XZ planechanges, the outer shapes (outlines) of the bucket 8 in the respectivecross-sections are substantially the same. However, in the case of atilt bucket, the outer shape of the bucket 8 in the cross-sectionparallel to the XZ plane changes according to the Y coordinate and thetilt (tilt angle δ) of the bucket 8. Due to this, when the bucket 8 istilted, the distance between the target excavation landform and thebucket 8 and the outer shape of the bucket 8 may change and at least aportion of the bucket 8 may dig into the target excavation landform.Thus, unless the shape (cross-sectional shape in the XZ plane) of thebucket 8 for realizing limited excavation control is specified, it maybe difficult to perform the limited excavation control with highaccuracy.

In the present embodiment, the sensor controller 32 (2-dimensionalbucket calculation unit 283A) calculates the 2-dimensional bucket data Sindicating the outer shape of the cross-section of the bucket 8 alongthe working plane MP which serves as a control object. The work machinecontrol unit 26A of the work machine controller 26 derives the distanced between the target excavation landform and the bucket 8 based on the2-dimensional bucket data S and the 2-dimensional designed landform dataU along the working plane MP (step SP4) and performs limited excavationcontrol of the work machine 2 (step SP5). Moreover, as will be describedlater, the sensor controller 32 displays the target excavation landformand the like on the display unit 29 (step SP6). In this way, the controlobject is specified based on the working plane MP and the limitedexcavation control is performed with high accuracy.

Hereinafter, an example of a method of deriving the 2-dimensional bucketdata S will be described. FIG. 23 is a diagram schematicallyillustrating the work machine 2 according to the present embodiment. Theorigin of the local coordinate system is the reference position P0positioned at the revolution center of the revolving structure 3. Theposition of the distal end 8 a of the bucket 8 in the local coordinatesystem is Pa.

The work machine 2 includes a first joint that rotates about the boomshaft J1, a second joint that rotates about the arm shaft J2, a thirdjoint that rotates about the bucket shaft J3, and a fourth joint thatrotates about the tilt shaft J4. Moreover, as described above, the tiltshaft J4 is tilted in the θY direction with the rotation of the bucket 8about the bucket shaft J3. The movements of the respective joints can beexpressed by Expressions (1) to (6) below. Expression (1) is anexpression for performing coordinate conversion between the origin (thereference position) P0 and the boom foot. Expression (2) is anexpression for performing coordinate conversion between the boom footand the boom top. Expression (3) is an expression for performingcoordinate conversion between the boom top and the arm top. Expression(4) is an expression for performing coordinate conversion between thearm top and one end of the tilt shaft J4. Expression (5) is anexpression for performing coordinate conversion between one end and theother end of the tilt shaft J4. Expression (6) is an expression forperforming coordinate conversion between the other end of the tilt shaftJ4 and the bucket 8.

$\begin{matrix}{T_{local}^{{boom}\text{-}{foot}} = \begin{pmatrix}1 & 0 & 0 & x_{{boom}\text{-}{foot}} \\0 & 1 & 0 & y_{{boom}\text{-}{foot}} \\0 & 0 & 1 & z_{{boom}\text{-}{foot}} \\0 & 0 & 0 & 1\end{pmatrix}} & (1) \\{T_{{boom}\text{-}{foot}}^{{boom}\text{-}{top}} = {\begin{pmatrix}{\cos \mspace{14mu} \theta_{boom}} & 0 & {\sin \mspace{14mu} \theta_{boom}} & 0 \\0 & 1 & 0 & 0 \\{{- \sin}\mspace{14mu} \theta_{boom}} & 0 & {\cos \mspace{14mu} \theta_{boom}} & 0 \\0 & 0 & 0 & 1\end{pmatrix}\begin{pmatrix}1 & 0 & 0 & 0 \\0 & 1 & 0 & 0 \\0 & 0 & 1 & L_{boom} \\0 & 0 & 0 & 1\end{pmatrix}}} & (2) \\{T_{{boom}\text{-}{top}}^{{arm}\text{-}{top}} = {\begin{pmatrix}{\cos \mspace{14mu} \theta_{arm}} & 0 & {\sin \mspace{14mu} \theta_{arm}} & 0 \\0 & 1 & 0 & 0 \\{{- \sin}\mspace{14mu} \theta_{arm}} & 0 & {\cos \mspace{14mu} \theta_{arm}} & 0 \\0 & 0 & 0 & 1\end{pmatrix}\begin{pmatrix}1 & 0 & 0 & 0 \\0 & 1 & 0 & 0 \\0 & 0 & 1 & L_{arm} \\0 & 0 & 0 & 1\end{pmatrix}}} & (3) \\{T_{{arm}\text{-}{top}}^{{tilt}_{—}A} = {\begin{pmatrix}{\cos \left( {\theta_{bucket} + \theta_{{tilt}_{—}y}} \right)} & 0 & {\sin \left( {\theta_{bucket} + \theta_{{tilt}_{—}y}} \right)} & 0 \\0 & 1 & 0 & 0 \\{- {\sin \left( {\theta_{bucket} + \theta_{{tilt}_{—}y}} \right)}} & 0 & {\cos \left( {\theta_{bucket} + \theta_{{tilt}_{—}y}} \right)} & 0 \\0 & 0 & 0 & 1\end{pmatrix}\begin{pmatrix}1 & 0 & 0 & 0 \\0 & 1 & 0 & 0 \\0 & 0 & 1 & L_{tilt} \\0 & 0 & 0 & 1\end{pmatrix}}} & (4) \\{T_{{tilt}_{—}A}^{{tilt}_{—}B} = {\begin{pmatrix}1 & 0 & 0 & 0 \\0 & {\cos \mspace{14mu} \theta_{{tilt}_{—}x}} & {{- \sin}\mspace{20mu} \theta_{{tilt}_{—}x}} & 0 \\0 & {\sin \mspace{14mu} \theta_{{tilt}_{—}x}} & {\cos \mspace{14mu} \theta_{{tilt}_{—}x}} & 0 \\0 & 0 & 0 & 1\end{pmatrix}\begin{pmatrix}1 & 0 & 0 & {- L_{{tilt}_{—}x}} \\0 & 1 & 0 & 0 \\0 & 0 & 1 & 0 \\0 & 0 & 0 & 1\end{pmatrix}}} & (5) \\{T_{{tilt}_{—}B}^{bucket} = {\begin{pmatrix}1 & 0 & 0 & 0 \\0 & 1 & 0 & 0 \\0 & 0 & 1 & L_{{bucket}_{—}{corrected}} \\0 & 0 & 0 & 1\end{pmatrix}\begin{pmatrix}{\cos \left( {- \theta_{{tilt}_{—}y}} \right)} & 0 & {\sin \left( {- \theta_{{tilt}_{—}y}} \right)} & 0 \\0 & 1 & 0 & 0 \\{- {\sin \left( {- \theta_{{tilt}_{—}y}} \right)}} & 0 & {\cos \left( {- \theta_{{tilt}_{—}y}} \right)} & 0 \\0 & 0 & 0 & 1\end{pmatrix}}} & (6)\end{matrix}$

In Expressions (1) to (6), xboom-foot, yboom-foot, and zboom-foot arethe coordinates of the boom foot in the local coordinate system. Lboomcorresponds to the boom length L1. Larm corresponds to the arm lengthL2. Lbucket_corrected is a corrected bucket length illustrated in FIG.2. Ltilt corresponds to the tilt length L4. θboom corresponds to theboom angle α. θarm corresponds to the arm angle β. θbucket correspondsto the bucket angle γ. θtilt_x corresponds to the tilt angle δ. θtilt_yis the angle illustrated in FIG. 2.

Thus, the coordinates (xarm-top, yarm-top, and zarm-top) of the arm topin relation to the origin of the local coordinate system are derivedfrom Expression (7) below.

$\begin{matrix}{{\begin{pmatrix}x_{{arm}\text{-}{top}} \\y_{{arm}\text{-}{top}} \\z_{{arm}\text{-}{top}} \\1\end{pmatrix} = {T_{local}^{{arm}\text{-}{top}}\begin{pmatrix}0 \\0 \\0 \\1\end{pmatrix}}}{{where},{T_{local}^{{arm}\text{-}{top}} = {T_{local}^{{boom}\text{-}{foot}}T_{{boom}\text{-}{foot}}^{{boom}\text{-}{top}}T_{{boom}\text{-}{top}}^{{arm}\text{-}{top}}}}}} & (7)\end{matrix}$

here

The shape data of the bucket 8 includes the cutting edge 8 a of thebucket 8 and the coordinate data of a plurality of positions (points) ofthe outer surface of the bucket 8. In the present embodiment, asillustrated in FIG. 24, the shape data of the bucket 8 includes firstoutline data of the outer surface of the bucket 8 at one end in thewidth direction of the bucket 8 and second outline data of the outersurface of the bucket 8 at the other end. The first outline dataincludes the coordinates of six outline points J at one end of thebucket 8. The second outline data includes the coordinates of sixoutline points K at the other end of the bucket 8. The coordinates ofthe outline points J and the coordinates of the outline points K are thecoordinate (position Pa) of the distal end 8 a and reference coordinatedata. Due to the shape data of the bucket 8, the positional relationbetween the coordinate of the distal end 8 a, the coordinates of theoutline points J, and the coordinates of the outline points K is known.Thus, by calculating the positional relation between the origin of thelocal coordinate system and the coordinate of the distal end 8 a, thecoordinates of the outline points J and the outline points K in relationto the origin of the local coordinate system can be calculated.

When the shape data (the coordinates of the outline) of the bucket 8 is(xbucket-outline, ybucket-outline, zbucket-outline), the coordinate ofthe outline points of the bucket 8 are derived from Expression (8)below.

$\begin{matrix}{{\begin{pmatrix}x_{n} \\y_{n} \\z_{n} \\1\end{pmatrix} = {T_{local}^{tooth}\begin{pmatrix}x_{{bucket}\text{-}{outline}} \\y_{{bucket}\text{-}{outline}} \\z_{{bucket}\text{-}{outline}} \\1\end{pmatrix}}}{where},{T_{local}^{tooth} = {T_{local}^{{boom}\text{-}{foot}}T_{{boom}\text{-}{foot}}^{{boom}\text{-}{top}}T_{{boom}\text{-}{top}}^{{arm}\text{-}{top}}T_{{arm}\text{-}{top}}^{{tilt}_{—}A}T_{{tilt}_{—}A}^{{tilt}_{—}B}T_{{tilt}_{—}B}^{bucket}}}} & (8)\end{matrix}$

here

In the present embodiment, the number of outline points J and K is 12.When the coordinates of the outline points J and K of the shape data ofthe bucket 8 are (x1, y1, z1), (x2, y2, z2), . . . , and (x12, y12,z12), the coordinates (x1′, y1′, z1′), (x2′, y2′, z2′), . . . , and(x12′, y12′, z12′) of the outline points J and K of the bucket 8 inrelation to the origin are derived from Expression (9) below.

$\begin{matrix}{\begin{pmatrix}x_{1}^{\prime} & x_{2}^{\prime} & \cdots & x_{12}^{\prime} \\y_{1}^{\prime} & y_{2}^{\prime} & \cdots & y_{12}^{\prime} \\z_{1}^{\prime} & z_{2}^{\prime} & \cdots & z_{12}^{\prime} \\1 & 1 & \cdots & 1\end{pmatrix} = {T_{local}^{bucket}\begin{pmatrix}x_{1} & x_{2} & \cdots & x_{12} \\y_{1} & y_{2} & \cdots & y_{12} \\z_{1} & z_{2} & \cdots & z_{12} \\1 & 1 & \cdots & 1\end{pmatrix}}} & (9)\end{matrix}$

After the coordinates of the plurality of outline points J and K arecalculated based on the work machine angle data, the work machinedimension data, the shape data of the bucket 8, and the tilt angle data,the calculation unit 28A calculates the 2-dimensional bucket data Sindicating the outer shape of the bucket 8 in the working plane MP.

FIG. 25 is a diagram schematically illustrating the relation between theoutline points J and K and the working plane MP. As described above,when the coordinates of the plurality of outline points Ji (i=1, 2, 3,4, 5, 6) and the plurality of outline points Ki (i=1, 2, 3, 4, 5, 6) inthe local coordinate system are calculated, the lines Hi (i=1, 2, 3, 4,5, 6) connecting the outline points Li and Ki are calculated. Moreover,the position (Y coordinate) of the working plane MP in the directionparallel to the bucket shaft J3 is designated in step SP2. Thus, thecalculation unit 28A (the 2-dimensional bucket data calculation unit283A) can calculate the 2-dimensional bucket data S indicating the outershape of the bucket 8 in the working plane MP based on the nodal pointsNi (i=1, 2, 3, 4, 5, 6) between the working plane MP and the lines Hi.In this way, in the present embodiment, the calculation unit 28A cancalculate the 2-dimensional bucket data S including the plurality ofoutline points (nodal points) Ni based on the first outline point dataincluding the coordinate data of the plurality of outline points Ji inthe local coordinate system, the second outline point data including thecoordinate data of the plurality of outline points Ki in the localcoordinate system, and the position of the working plane MP in relationto the Y-axis direction parallel to the bucket shaft J3.

The above-described method of deriving the coordinates of the outlinepoints Ji and Ki in the local coordinate system is an example. The2-dimensional bucket data S may be calculated by calculating thecoordinates of the outline points Ji and Ki in the local coordinatesystem when the work machine 2 is driven based on the work machine angledata including the boom angle α, the arm angle β, and the bucket angleγ, the work machine dimension data including the boom length L1, the armlength L2, the bucket length L3, and the tilt length L4, the shape dataof the bucket 8 including the width dimension L5 of the bucket 8, thecoordinate data of the outline points Ji and Ki, and the tilt angle dataindicating the tilt angle δ. A change in the coordinates of the outlinepoints J and K associated with a change in the tilt shaft angle ε can beuniquely calculated based on the bucket angle γ and the tilt length L4.

For example, the coordinate of the cutting edge 8 a in the localcoordinate system of the bucket 8 having no tilting mechanism can bederived from the dimensions of the work machine 2 (the dimensions of theboom 6, the dimensions of the arm 7, and the dimensions of the bucket 8)and the work machine angles (the rotation angle α, the rotation angle β,and the rotation angle γ). After the coordinate of the cutting edge 8 ofthe bucket 8 or the coordinate of the arm top is calculated, the outlinepoints Ji, the outline points Ki, and the 2-dimensional bucket data Smay be calculated based on the tilt length L4, the width dimension L5,the tilt angle δ, and the shape data of the bucket 8 by referring to thecoordinate.

The 2-dimensional bucket data S indicates the present position of thebucket 8 in the local coordinate system. That is, the 2-dimensionalbucket data S includes the bucket position data indicating the presentposition of the bucket 8 in the working plane MP. The 2-dimensionalbucket data S is output from the display controller 28 to the workmachine controller 26. The work machine control unit 26A of the workmachine controller 26 controls the work machine 2 based on the2-dimensional bucket data S (step SP5).

The work machine controller 26 acquires the 2-dimensional bucket data Sand the target excavation landform data U from the display controller28. The work machine control unit 26A of the work machine controller 26limits the speed of the boom 6 so that the speed at which the bucket 8approaches the target excavation landform decreases according to thedistance d between the bucket 8 and the target excavation landform inthe working plane MP based on the target excavation landform data U andthe 2-dimensional bucket data S including the bucket position data. Thework machine control unit 26A determines a speed limit according to thedistance between the bucket 8 and the target excavation landform basedon the target excavation landform data U and the 2-dimensional bucketdata including the bucket position data and controls the work machine 2so that the speed at which the work machine 2 approaches the targetexcavation landform is equal to or smaller than the speed limit.

Next, an example of limited excavation control according to the presentembodiment will be described with reference to the flowchart of FIG. 26and the schematic diagrams of FIGS. 27 to 34. FIG. 26 is a flowchartillustrating an example of limited excavation control according to thepresent embodiment.

As described above, the target excavation landform is set (step SA1).After the target excavation landform is set, the work machine controller26 determines the target speed Vc of the work machine 2 (step SA2). Thetarget speed Vc of the work machine 2 includes a boom target speedVc_bm, an arm target speed Vc_am, and a bucket target speed Vc_bkt. Theboom target speed Vc_bm is the speed of the cutting edge 8 a when theboom cylinder 10 only is driven. The arm target speed Vc_am is the speedof the cutting edge 8 a when the arm cylinder 11 only is driven. Thebucket target speed Vc_bkt is the speed of the cutting edge 8 a when thebucket cylinder 12 only is driven. The boom target speed Vc_bm iscalculated based on the amount of boom operation. The arm target speedVc_am is calculated based on the amount of arm operation. The buckettarget speed Vc_bkt is calculated based on the amount of bucketoperation.

Target speed information that defines the relation between the boomtarget speed Vc_bm and the pilot pressure acquired from the pressuresensor 66A or 66B corresponding to the amount of boom operation isstored in a storage unit of the work machine controller 26. The workmachine controller 26 determines the boom target speed Vc_bmcorresponding to the amount of boom operation based on the target speedinformation. The target speed information is a map in which themagnitude of the boom target speed Vc_bm corresponding to the amount ofboom operation, for example, is described. The target speed informationmay be in the form of a table, a numerical expression, or the like. Thetarget speed information includes information that defines the relationbetween the arm target speed Vc_am and the pilot pressure acquired fromthe pressure sensor 66A or 66B corresponding to the amount of armoperation. The target speed information includes information thatdefines the relation between the bucket target speed Vc_bkt and thepilot pressure acquired from the pressure sensor 66A or 66Bcorresponding to the amount of bucket operation. The work machinecontroller 26 determines the arm target speed Vc_am corresponding to theamount of arm operation based on the target speed information. The workmachine controller 26 determines the bucket target speed Vc_bktcorresponding to the amount of bucket operation based on the targetspeed information.

As illustrated in FIG. 27, the work machine controller 26 converts theboom target speed Vc_bm into a speed component (vertical speedcomponent) Vcy_bm in the direction vertical to the surface of the targetexcavation landform and a speed component (horizontal speed component)Vcx_bm in the direction parallel to the surface of the target excavationlandform (step SA3).

The work machine controller 26 calculates an inclination of the verticalaxis (the revolution axis AX of the revolving structure 3) of the localcoordinate system with respect to the vertical axis of the globalcoordinate system and an inclination in the vertical direction of thesurface of the target excavation landform with respect to the verticalaxis of the global coordinate system from the reference position data P,the target excavation landform, and the like. The work machinecontroller 26 calculates an angle β1 indicating the inclination betweenthe vertical axis of the local coordinate system and the verticaldirection of the surface of the target excavation landform from theseinclinations.

As illustrated in FIG. 28, the work machine controller 26 converts theboom target speed Vc_bm into a speed component VL1_bm in the verticalaxis direction of the local coordinate system and a speed componentVL2_bm in the horizontal axis direction according to the theorem oftrigonometric function from an angle θ2 between the vertical axis of thelocal coordinate system and the direction of the boom target speedVc_bm.

As illustrated in FIG. 9, the work machine controller 26 converts thespeed component VL1_bm in the vertical axis direction of the localcoordinate system and the speed component VL2_bm in the horizontal axisdirection into a vertical speed component Vcy_bm and a horizontal speedcomponent Vcx_bm with respect to the target excavation landformaccording to the theorem of trigonometric function from the inclinationβ1 between the vertical axis of the local coordinate system and thevertical direction of the surface of the target excavation landform.Similarly, the work machine controller 26 converts the arm target speedVc_am into a vertical speed component Vcy_am and a horizontal speedcomponent Vcx_am in the vertical axis direction of the local coordinatesystem. The work machine controller 26 converts the bucket target speedVc_bkt into a vertical speed component Vcy_bkt and a horizontal speedcomponent Vcx_bkt in the vertical axis direction of the local coordinatesystem.

As illustrated in FIG. 30, the work machine controller 26 acquires thedistance d between the cutting edge 8 a of the bucket 8 and the targetexcavation landform (step SA4). The work machine controller 26calculates the shortest distance d between the surface of the targetexcavation landform and the cutting edge 8 a of the bucket 8 from theposition information of the cutting edge 8 a, the target excavationlandform, and the like. In the present embodiment, the limitedexcavation control is executed based on the shortest distance d betweenthe surface of the target excavation landform and the cutting edge 8 aof the bucket 8.

The work machine controller 26 calculates an overall speed limit Vcy_lmtof the work machine 2 based on the distance d between the surface of thetarget excavation landform and the cutting edge 8 a of the bucket 8(step SA5). The overall speed limit Vcy_lmt of the work machine 2 is anallowable moving speed of the cutting edge 8 a in the direction in whichthe cutting edge 8 a of the bucket 8 approaches the target excavationlandform. Speed limit information that defines the relation between thedistance d and the speed limit Vcy_lmt is stored in the storage unit ofthe work machine controller 26.

FIG. 31 illustrates an example of the speed limit information accordingto the present embodiment. In the present embodiment, the distance d hasa positive value when the cutting edge 8 a is positioned on the outerside of the surface of the target excavation landform (that is, on theside close to the work machine 2 of the excavator 100), and the distanced has a negative value when the cutting edge 8 a is positioned on theinner side of the surface of the target excavation landform (that is, onthe inner side of the excavation object than the target excavationlandform). As illustrated in FIG. 30, the distance d has a positivevalue when the cutting edge 8 a is positioned above the surface of thetarget excavation landform. The distance d has a negative value when thecutting edge 8 a is positioned under the surface of the targetexcavation landform. Moreover, the distance d has a positive value whenthe cutting edge 8 a is positioned at such a position that the cuttingedge 8 a does not dig into the target excavation landform. The distanced has a negative value when the cutting edge 8 a is positioned at such aposition that the cutting edge 8 a digs into the target excavationlandform. The distance d is 0 when the cutting edge 8 a is positioned onthe target excavation landform (that is, when the cutting edge 8 a is incontact with the target excavation landform).

In the present embodiment, the speed has a positive value when thecutting edge 8 a moves from the inner side of the target excavationlandform toward the outer side, and the speed has a negative value whenthe cutting edge 8 a moves from the outer side of the target excavationlandform toward the inner side. That is, the speed has a positive valuewhen the cutting edge 8 a moves toward the upper side of the targetexcavation landform, and the speed has a negative value when the cuttingedge 8 a moves toward the lower side of the target excavation landform.

In the speed limit information, an inclination of the speed limitVcy_lmt when the distance d is between d1 and d2 is smaller than aninclination when the distance d is equal to or larger than d1 or equalto or smaller than d2. d1 is larger than 0. d2 is smaller than 0. Inoperations near the surface of the target excavation landform, in orderto set the speed limit more accurately, the inclination when thedistance d is between d1 and d2 is smaller than the inclination when thedistance d is equal to or larger than d1 or equal to or smaller than d2.The speed limit Vcy_lmt has a negative value when the distance d isequal to or larger than d1, and the larger the distance d, the smallerthe speed limit Vcy_lmt. That is, when the distance d is equal to orlarger than d1, the farther the cutting edge 8 a above the targetexcavation landform from the surface of the target excavation landform,the larger the speed of moving toward the lower side of the targetexcavation landform and the larger the absolute value of the speed limitVcy_lmt. When the distance d is equal to or smaller than 0, the speedlimit Vcy_lmt has a positive value, and the smaller the distance d, thelarger the speed limit Vcy_lmt. That is, when the distance d of thecutting edge 8 a of the bucket 8 from the target excavation landform isequal to or smaller than 0, the farther the cutting edge 8 a on thelower side of the target excavation landform from the target excavationlandform, the larger the speed of moving toward the upper side of thetarget excavation landform, and the larger the absolute value of thespeed limit Vcy_lmt.

When the distance d is equal to or larger than a predetermined valuedth1, the speed limit Vcy_lmt is Vmin. The predetermined value dth1 is apositive value and is larger than d1. Vmin is smaller than a smallestvalue of the target speed. That is, when the distance d is equal to orlarger than the predetermined value dth1, the operation of the workmachine 2 is not limited. Thus, when the cutting edge 8 a is separatedgreatly from the target excavation landform on the upper side of thetarget excavation landform, the operation of the work machine 2 is notlimited (that is, the limited excavation control is not performed). Whenthe distance d is smaller than the predetermined value dth1, theoperation of the work machine 2 is limited. When the distance d issmaller than the predetermined value dth1, the operation of the boom 6is limited.

The work machine controller 26 calculates a vertical speed component(limited vertical speed component) Vcy_bm_lmt of the speed limit of theboom 6 from the overall speed limit Vcy_lmt of the work machine 2, thearm target speed Vc_am, and the bucket target speed Vc_bkt (step SA6).

As illustrated in FIG. 12, the work machine controller 26 calculates thelimited vertical speed component Vcy_bm_lmt of the boom 6 by subtractingthe vertical speed component Vcy_am of the arm target speed and thevertical speed component Vcy_bkt of the bucket target speed from theoverall speed limit Vcy_lmt of the work machine 2.

As illustrated in FIG. 33, the work machine controller 26 converts thelimited vertical speed component Vcy_bm_lmt of the boom 6 into a speedlimit (boom speed limit) Vc_bm_lmt (step SA7). The work machinecontroller 26 obtains a relation between a direction vertical to thesurface of the target excavation landform and the direction of the boomspeed limit Vc_bm_lmt from a rotation angle α of the boom 6, a rotationangle β of the arm 7, a rotation angle of the bucket 8, vehicle bodyposition data P, the target excavation landform, and the like andconverts the limited vertical speed component Vcy_bm_lmt of the boom 6into a boom speed limit Vc_bm_lmt. This calculation is performed in areverse order to that of the calculation of calculating the verticalspeed component Vcy_bm in the direction vertical to the surface of thetarget excavation landform from the boom target speed Vc_bm. After that,a cylinder speed corresponding to a boom intervention amount isdetermined, and a release command corresponding to the cylinder speed isoutput to the control valve 27C.

The pilot pressure based on the lever operation is filled in an oilpassage 43B and the pilot pressure based on boom intervention is filledin an oil passage 43C. A shuttle valve 51 selects the oil passage havingthe larger pressure (step SA8).

For example, when the boom 6 is lowered, and the magnitude of the boomspeed limit Vc_bm_lmt in the downward direction of the boom 6 is smallerthan the magnitude of the boom target speed Vc_bm in the downwarddirection, limiting conditions are satisfied. Moreover, when the boom 6is raised, and the magnitude of the boom speed limit Vc_bm_lmt in theupward direction of the boom 6 is larger than the magnitude of the boomtarget speed Vc_bm in the upward direction, the limiting conditions aresatisfied.

The work machine controller 26 controls the work machine 2. Whencontrolling the boom 6, the work machine controller 26 controls the boomcylinder 10 by transmitting a boom command signal to the control valve27C. The boom command signal has a current value corresponding to a boomcommand speed. If necessary, the work machine controller 26 controls thearm 7 and the bucket 8. The work machine controller 26 controls the armcylinder 11 by transmitting an arm command signal to the control valve27. The arm command signal has a current value corresponding to the armcommand speed. The work machine controller 26 controls the bucketcylinder 12 by transmitting a bucket command signal to the control valve27. The bucket command signal has a current value corresponding to thebucket command speed.

When the limiting conditions are not satisfied, the shuttle valve 51selects the supply of operating oil from the oil passage 43B, and anormal operation is performed (step SA9). The work machine controller 26operates the boom cylinder 10, the arm cylinder 11, and the bucketcylinder 12 according to the amount of boom operation, the amount of armoperation, and the amount of bucket operation, respectively. The boomcylinder 10 operates at the boom target speed Vc_bm. The arm cylinder 11operates at the arm target speed Vc_am. The bucket cylinder 12 operatesat the bucket target speed Vc_bkt.

When the limiting conditions are satisfied, the shuttle valve 51 selectsthe supply of operating oil from the oil passage 43C, and the limitedexcavation control is executed (step SA10).

The limited vertical speed component Vcy_bm_lmt of the boom 6 iscalculated by subtracting the vertical speed component Vcy_am of the armtarget speed and the vertical speed component Vcy_bkt of the buckettarget speed from the overall speed limit Vcy_lmt of the work machine 2.Thus, when the overall speed limit Vcy_lmt of the work machine 2 issmaller than the sum of the vertical speed component Vcy_am of the armtarget speed and the vertical speed component Vcy_bkt of the buckettarget speed, the limited vertical speed component Vcy_bm_lmt of theboom 6 has a negative value, in which case the boom is raised.

Thus, the boom speed limit Vc_bm_lmt has a negative value. In this case,the work machine controller 27 lowers the boom 6 at a speed lower thanthe boom target speed Vc_bm. Thus, it is possible to prevent the bucket8 from digging into the target excavation landform while suppressing thesense of incongruity the operator might feel.

When the overall speed limit Vcy_lmt of the work machine 2 is largerthan the sum of the vertical speed component Vcy_am of the arm targetspeed and the vertical speed component Vcy_bkt of the bucket targetspeed, the limited vertical speed component Vcy_bm_lmt of the boom 6 hasa positive value. Thus, the boom speed limit Vc_bm_lmt has a positivevalue. In this case, even when the operating device 25 is operated in adirection where the boom 6 is lowered, the work machine controller 26raises the boom 6. Thus, it is possible to quickly suppress expansion ofa digged area of the target excavation landform.

When the cutting edge 8 a is positioned above the target excavationlandform, the closer the cutting edge 8 a approaches the targetexcavation landform, the smaller the absolute value of the limitedvertical speed component Vcy_bm_lmt of the boom 6, and the smaller theabsolute value of the speed component (limited horizontal speedcomponent) Vcx_bm_lmt of the speed limit of the boom 6 in the directionparallel to the surface of the target excavation landform. Thus, whenthe cutting edge 8 a is positioned above the target excavation landform,the closer the cutting edge 8 a approaches the target excavationlandform, the more the speed of the boom 6 in the direction vertical tothe surface of the target excavation landform and the speed of the boom6 in the direction parallel to the surface of the target excavationlandform are decelerated. When the left operating lever 25L and theright operating lever 25R are operated simultaneously by the operator ofthe excavator 100, the boom 6, the arm 7, and the bucket 8 are operatedsimultaneously. In this case, the above-described control when targetspeeds Vc_bm, Vc_am, and Vc_bkt of the boom 6, the arm 7, and the bucket8 are input will be described below.

FIG. 34 illustrates an example of a change in the speed limit of theboom 6 when the distance d between the target excavation landform andthe cutting edge 8 a of the bucket 8 is smaller than the predeterminedvalue dth1 and the cutting edge 8 a of the bucket 8 moves from theposition Pn1 to the position Pn2. The distance between the cutting edge8 a and the target excavation landform at the position Pn2 is smallerthan the distance between the cutting edge 8 a and the target excavationlandform at the position Pn1. Due to this, the limited vertical speedcomponent Vcy_bm_lmt2 of the boom 6 at the position Pn2 is smaller thanthe limited vertical speed component Vcy_bm_lmt1 of the boom 6 at theposition Pn1. Thus, the boom speed limit Vc_bm_lmt2 at the position Pn2is smaller than the boom speed limit Vc_bm_lmt1 at the position Pn1.Moreover, the limited horizontal speed component Vcx_bm_lmt2 of the boom6 at the position Pn2 is smaller than the limited horizontal speedcomponent Vcx_bm_lmt1 of the boom 6 at the position Pn1. However, inthis case, the arm target speed Vc_am and the bucket target speed Vc_bktare not limited. Due to this, the vertical speed component Vcy_am andthe horizontal speed component Vcx_am of the arm target speed and thevertical speed component Vcy_bkt and the horizontal speed componentVcx_bkt of the bucket target speed are not limited.

As described above, since no limitation is applied to the arm 7, achange in the amount of arm operation corresponding to the operator'sintention to excavate is reflected as a change in the speed of thecutting edge 8 a of the bucket 8. Thus, the present embodiment cansuppress the sense of incongruity during the excavation operation of theoperator while suppressing expansion of a digged area of the targetexcavation landform.

In this manner, in the present embodiment, the work machine controller26 limits the speed of the boom 6 based on the target excavationlandform indicating the designed landform which is a target shape of anexcavation object and the cutting edge position data S indicating theposition of the cutting edge 8 a of the bucket 8 so that a relativespeed at which the bucket 8 approaches the target excavation landformdecreases according to the distance d between the target excavationlandform and the cutting edge 8 a of the bucket 8. The work machinecontroller 26 determines the speed limit according to the distance dbetween the target excavation landform and the cutting edge 8 a of thebucket 8 based on the target excavation landform indicating the designedlandform which is a target shape of an excavation object and the cuttingedge position data S indicating the position of the cutting edge 8 a ofthe bucket 8 and controls the work machine 2 so that the speed in thedirection in which the work machine 2 approaches the target excavationlandform is equal to or smaller than the speed limit. In this way,limited excavation control on the cutting edge 8 a is executed, and theposition of the cutting edge 8 a in relation to the target excavationlandform is automatically adjusted.

In the limited excavation control (intervention control), a controlsignal is output to the control valve 27 connected to the boom cylinder10 and the position of the boom 6 is controlled so that digging of thecutting edge 8 a into the target excavation landform is suppressed. Theintervention control is executed when the relative speed Wa is largerthan the speed limit V. The intervention control is not executed whenthe relative speed Wa is smaller than the speed limit V. The fact thatthe relative speed Wa is smaller than the speed limit V includes thefact that the bucket 8 moves in relation to the target excavationlandform so that the bucket 8 is separated from the target excavationlandform.

In the present embodiment, the 2-dimensional bucket data S may be usedfor deriving the relative position between the bucket 8 and the targetexcavation landform and the 2-dimensional bucket data S of which thecoordinate is converted from the local coordinate system to a polarcoordinate system may be used for control of the work machine 2. Forexample, as illustrated in FIG. 35, the arm top (bucket shaft J3) may bethe origin of the polar coordinate system and a plurality of outlinepoints A, B, C, D, and E of the bucket 8 in the working plane MP may berepresented by the distance to the origin and the angles θA, θB, θC, θD,and θE with respect to a reference line. The reference line may be aline connecting the bucket shaft J3 and the distal end 8 a of the bucket8. By using the polar coordinate system, the target excavation landform,the distal end 8 a of the bucket 8, and the outline of the cross-sectionof the bucket 8 in the working plane MP when the bucket 8 is tilted canbe calculated properly, the distance between the target excavationlandform and the distal end 8 a of the bucket 8 can be calculatedaccurately, and the accuracy of excavation control can be secured.

As described above, in the present embodiment, the tilt angle sensor 70detects the tilt angle of the bucket 8 with respect to the horizontalplane in the global coordinate system. The tilt angle sensor 70 isdisposed in the bucket 8, and when the bucket 8 is inclined with respectto the horizontal plane, the tilt angle sensor 70 outputs tilt angledata corresponding to the inclination angle to the acquisition unit 28C.

FIG. 36 is a schematic diagram for describing the principle of the tiltangle sensor 70 according to the present embodiment. As illustrated inFIG. 36, the tilt angle sensor 70 detects the tilt angle (rotation angleand inclination angle) with respect to the horizontal plane (XgYg plane)in the global coordinate system. That is, the tilt angle sensor 37 is abiaxial angle sensor that detects inclination angles in relation to thetwo θXg and θYg directions. The tilt angle sensor 70 has a referencesurface 70R and detects an inclination angle of the reference surface70R with respect to the horizontal plane.

The bucket 8 has an installation surface which is located near the tiltpin and on which the tilt angle sensor 70 is provided. When theinstallation surface of the bucket 8 is parallel to the horizontalplane, the bucket 8 is in an initial attitude (horizontal attitude).When the bucket 8 is in an initial attitude, the tilt angle sensor 70 isprovided on the installation surface of the bucket 8 so that thereference surface 70R is parallel to the horizontal plane (installationsurface).

In a state where the reference surface 70R and the horizontal plane areparallel to each other, the detection accuracy of the tilt angle sensor70 detecting the inclination angle is highest. In a state where thereference surface 70R and the horizontal plane are orthogonal to eachother, the detection accuracy of the tilt angle sensor 70 detecting theinclination angle is lowest. That is, the detection accuracy of the tiltangle sensor 70 increases when the reference surface 70R is horizontaland the detection accuracy of the tilt angle sensor 70 decreases whenthe reference surface 70R is vertical.

Thus, when the attitude of the bucket 8 provided in the tilt anglesensor 70 changes, the detection accuracy of the tilt angle sensor 70changes. For example, when the bucket 8 in the initial attitude rotatesabout the tilt shaft J4, the detection accuracy of the tilt angle sensor70 provided in the bucket 8 may decrease. Moreover, when the attitude ofthe bucket 8 changes due to the raising operation or the loweringoperation of at least one of the boom 6 and the bucket 7, the detectionaccuracy of the tilt angle sensor 70 provided in the bucket 8 maydecrease. For example, when the work machine 2 is extended and the angleof the reference surface 70R approaches the vertical direction, thedetection accuracy of the tilt angle sensor 70 decreases.

Moreover, the bucket 8 rotates about the tilt shaft J4 with the drivingof the tilt cylinder 30. The bucket 8 is inclined in relation to thehorizontal plane according to the raising operation or the loweringoperation of at least one of the boom 6 and the arm 7 as well as thedriving of the tilt cylinder 30. Due to this, even when the tiltcylinder 30 is not driven, the tilt angle sensor 70 outputs the tiltangle data based on the raising operation or the lowering operation ofat least one of the boom 6 and the arm 7 to the acquisition unit 28C.

In this manner, the tilt angle data output from the tilt angle sensor 70includes a tilt angle component based on the raising operation or thelowering operation of at least one of the boom 6 and the arm 7 as wellas a tilt angle component corresponding to the stroke length of the tiltcylinder 30. Due to this, it may be difficult to acquire accurate tiltangle data based on the driving of the tilt cylinder 30 using the tiltangle sensor 70.

As described above, the tilt angle sensor 70 is a biaxial (θXg and θYgdirection) angle sensor in relation to the horizontal plane, and may notbe possible to detect an accurate tilt angle depending on the attitudeof the bucket 8, for example, when the angle of the reference surface70R of the tilt angle sensor 70 approaches the vertical direction of theglobal coordinate system. That is, it may be difficult to secure dynamicdetection accuracy of the tilt angle sensor 70 based on the driving ofthe work machine 2 and static detection accuracy of the tilt anglesensor 70 based on the attitude of the bucket 8, and to output anaccurate detection result.

As a result, when limited excavation control is executed based on thetilt angle data (monitor data) acquired in realtime from the tilt anglesensor 70, limited excavation control may be performed based on the tiltangle data output from the tilt angle sensor 70 having decreaseddetection accuracy and the excavation accuracy may decrease.

In the present embodiment, the detection value of the tilt angle sensor70 can be fixed according to a fixing command. In this way, according toan operation of an operator, the tilt angle data output from the tiltangle sensor 70 to the acquisition unit 28C is fixed when the detectionaccuracy of the tilt angle sensor 70 is high (when the angle of thereference surface 70R approaches the horizontal direction), and thefixed data is determined. After that, the work machine 2 is controlledbased on the fixed data. In this way, even when the work machine 2 isdriven or the attitude of the bucket 8 changes after that, it ispossible to prevent limited excavation control from being performedbased on the tilt angle data output from the tilt angle sensor 70 havingdecreased detection accuracy.

In the present embodiment, a fixing command for fixing the tilt angledata is output to at least one of the work machine controller 26 and thesensor controller 32. When the fixing command is output, the tilt angledata is fixed and the fixed data is generated.

The control of the work machine 2 based on the fixed data is performeduntil the fixing command is disabled. The work machine control unit 26Acontrols the work machine 2 based on the fixed data until the fixingcommand is disabled. The fixing command is disabled when a fixingdisable command is output. When the fixing command is disabled, the tiltangle data is output in realtime from the tilt angle sensor 70 to thework machine controller 26 and the sensor controller 32. After thefixing command is disabled, the work machine 2 is controlled based onthe tilt angle data output from the tilt angle sensor 70.

The fixing command is output to the fixing unit 28D so that the workmachine 2 is controlled based on the fixed data in at least a portion ofthe period where the limited excavation control is performed. In thepresent embodiment, the fixing command is output to the fixing unit 28Dat the start of limited excavation control and is disabled at the end ofthe limited excavation control.

In the present embodiment, the limited excavation control periodincludes at least one of a period where a limited excavation controlmode is set and a limited excavation control state period.

The limited excavation control mode is set according to an operation ofthe input unit 36. In the present embodiment, the input unit 36 includesa button (excavation control mode switch button) for instructing whetherlimited excavation control is performed or not. When the excavationcontrol mode switch button is operated by the operator, a command signalcorresponding to at least one of the start and the end of the limitedexcavation control mode is output to the work machine controller 26.That is, according to the operation of the input unit 36, at least oneof a start command and an end command for the limited excavation controlmode is output to the work machine controller 26. The start time of thelimited excavation control mode is the time when the excavation controlmode switch button is operated so that the limited excavation controlmode starts. The ending time of the limited excavation control mode isthe time when the excavation control mode switch button is operated sothat the limited excavation control mode ends.

In the present embodiment, a fixing command is output according to anoperation of the excavation control mode switch button for starting thelimited excavation control. Moreover, a fixing disable command is outputaccording to an operation of the excavation control mode switch buttonfor ending the limited excavation control. That is, in the presentembodiment, a limited excavation control mode start command includes thefixing command. A limited excavation control mode ending commandincludes the fixing disable command. When the fixing command is output,the fixing command is output to the fixing unit 28D and the tilt angledata when the fixing command is output to the fixing unit 28D ismaintained (fixed).

The input unit 36 may include a dedicated button (tilt angle fixingbutton) capable of generating a command signal including a fixingdisable command and a fixing command for fixing the tilt angle data. Thecommand signal generated when the tilt angle fixing button is operatedis output to the sensor controller for controlling the tilt angle sensor70. For example, after the tilt angle fixing button is operated and thefixing command is output, the fixed data may be output from the tiltangle sensor 70 to the acquisition unit 28C.

The tilt angle fixing button may be operated and the fixing command maybe output before the limited excavation control mode starts (before theexcavation control mode switch button for starting the limitedexcavation control mode is operated). The tilt angle fixing button maybe operated and the fixing command may be output when the limitedexcavation control mode starts (when the excavation control mode switchbutton for starting the limited excavation control mode is operated).The tilt angle fixing button may be operated and the fixing command maybe output when the limited excavation control mode ends (when theexcavation control mode switch button for ending the limited excavationcontrol mode is operated). The tilt angle fixing button may be operatedand the fixing command may be output after the limited excavationcontrol mode ends (after the excavation control mode switch button forending the limited excavation control mode is operated).

The limited excavation control state includes a state where the relativespeed Wa of the cutting edge 8 a exceeds the speed limit V. The starttime of the limited excavation control state is the time when therelative speed Wa of the cutting edge 8 a exceeds the speed limit V. Theending time of the excavation control state is the time when therelative speed Wa of the cutting edge 8 a is equal to or smaller thanthe speed limit V.

The fixing command may be output from the work machine controller 26 tothe fixing unit 28D at the start time of the limited excavation controlstate. The fixing disable command may be output from the work machinecontroller 26 to the fixing unit 28D at the ending time of the limitedexcavation control state.

In the excavation operation, when the input unit 36 is operated by theoperator and the fixing command is output, the fixing unit 28D fixes thetilt angle data which is the monitor data of the tilt angle sensor 70based on the fixing command to generate fixed data.

The calculation unit 28A calculates the bucket position data indicatingthe present position of the bucket 8 based on the fixed data, the workmachine angle data, and the work machine dimension data. The workmachine control unit 26A executes limited excavation control of limitingthe speed of the boom 6 so that the speed at which the bucket 8approaches the target excavation landform according to the distancebetween the bucket 8 and the target excavation landform based on thetarget excavation landform and the bucket position data calculated usingthe fixed data.

That is, according to the above-described example, the calculation unit28A calculates the 2-dimensional bucket data S indicating the outershape of the bucket 8 in the working plane MP including the bucketposition data based on the work machine angle data, the work machinedimension data, the shape data of the bucket 8, and the fixed data, andthe work machine control unit 28 controls the work machine 2 based onthe 2-dimensional bucket data S.

In the present embodiment, the driving of the bucket 8 is inhibited inthe limited excavation control state period. That is, in the limitedexcavation control, the rotation of the bucket 8 about the tilt shaft J4is stopped. In the limited excavation control, the rotation of thebucket 8 about the bucket shaft J3 is not inhibited.

As described above, the work machine 2 includes the tilt cylinder 30capable of driving the bucket 8, and the bucket 8 rotates about the tiltshaft J4 according to the operation of the tilt cylinder 30. In thepresent embodiment, in limited excavation control, the drivinginhibiting unit 26B of the work machine controller 26 performs a drivinginhibiting process so that the tilt cylinder 30 does not operated.

As described above, the tilt cylinder 30 is operated by the operatingdevice 25 that includes the third operating lever 25P. The tilt cylinder30 operates according to an operation signal output from the operatingdevice 25. In the present embodiment, when an operation signal foroperating the tilt cylinder 30 is output from the operating device 25,the driving inhibiting unit 26B disables the operation signal outputfrom the operating device 25.

In the present embodiment, disabling the operation signal includesfixing the operation of the tilt cylinder 30 while maintaining the pilotpressure of the pilot pressure line 450. FIG. 37 is a diagramillustrating an example of the hydraulic system 300 according to thepresent embodiment.

As illustrated in FIG. 37, the hydraulic system 300 includes thedirection control valve 64 capable of adjusting the amount of operatingoil supplied to the tilt cylinder 30, the control valves 27D and 27Ethat adjust the pressure of the pilot oil supplied to the directioncontrol valve 64, the operation pedal 25F, the pump controller 34, andthe work machine controller 26.

The control valves 27D and 27E operate based on a control signal(driving inhibition signal) output from the driving inhibiting unit 26Bof the work machine controller 26. The control valve 27D is disposed inan oil passage between the shuttle valve 51A and the direction controlvalve 64. The control valve 27E is disposed in an oil passage betweenthe shuttle valve 51B and the direction control valve 64.

When a driving inhibiting process is performed, the driving inhibitingunit 26B of the work machine controller 26 outputs a driving inhibitionsignal based on a fixing command. Based on the driving inhibition signaloutput from the driving inhibiting unit 26B, a control signal is outputto the control valves 27D and 27E so that the oil passage 43 (43A and43B) is closed. In this way, the pilot pressure of the oil passage 43(the pilot pressure line) is maintained to a constant value. Thus, thespool of the direction control valve 64 does not move. Thus, the tiltcylinder 30 does not operate and the driving of the bucket 8 isinhibited. That is, the rotation of the bucket 8 about the tilt shaft J4is stopped (fixed).

The work machine 2 performs an excavation operation while maintainingthe attitude of the bucket 8 in relation to the rotation direction aboutthe tilt shaft J4 at the start time of the limited excavation controlstate. When the limited excavation control state ends (is disabled), theinhibition of the driving of the bucket 8 is disabled.

In the present embodiment, in the limited excavation control, the tiltangle data is fixed and fixed data is generated. Based on the fixeddata, when the bucket 8 rotates about the tilt shaft J4 in the limitedexcavation control state period, the possibility of the bucket 8 digginginto the target excavation landform increases. In the presentembodiment, in the limited excavation control state, the position of thebucket 8 in relation to the rotation direction about the tilt shaft J4as well as the tilt angle data are fixed. Due to this, a differencebetween the fixed data value and the actual tilt angle of the bucket 8is decreased and excavation following the target excavation landform ispossible.

The driving of the bucket 8 may be inhibited in the limited excavationcontrol mode period as well as the limited excavation control stateperiod.

In the limited excavation control, although the fixed data is generated,the driving of the bucket 8 may not be inhibited.

When the input unit 36 is operated by the operator in order to end thelimited excavation control mode, a fixing disable command is output. Inthis way, the excavation operation ends. A fixing disabling means may beindependent from inputting of the input unit 36 for ending theexcavation control mode.

[Display Unit]

FIG. 38 is a diagram illustrating an example of the display unit 29. Inthe present embodiment, the display unit 29 displays the 2-dimensionalbucket data S including the 2-dimensional designed landform data U andthe bucket position data. The display unit 29 displays at least one ofdistance data indicating the distance between the bucket 8 and thetarget excavation landform in the working plane MP and shape dataindicating the outer shape of the bucket 8 in the working plane MP.

The screen of the display unit 29 includes a front view 282 illustratingthe target excavation landform and the bucket 8 and a side view 281illustrating the target excavation landform and the bucket 8. The frontview 282 includes an icon 101 indicating the bucket 8 and a line 102indicating the cross-section of the target construction information.Moreover, the front view 282 includes distance data 291A indicating thedistance (the distance in the Z-axis direction) between the bucket 8 andthe target excavation landform and angle data 292A indicating the anglebetween the cutting edge 8 a and the target excavation landform.

The side view 281 includes an icon 103 indicating the bucket 8 and aline 104 indicating the surface of the target excavation landform in theworking plane MP. The icon 103 indicates the outer shape of the bucket 8in the working plane MP. Moreover, the side view 281 includes distancedata 292A indicating the distance (the shortest distance between thebucket 8 and the target excavation landform) between the bucket 8 andthe target excavation landform and angle data 292B indicating the anglebetween the bottom surface of the bucket 8 and the target excavationlandform.

[Effects]

As described above, according to the present embodiment, a fixingcommand means capable of outputting a fixing command when accurate tiltangle data is output from the tilt angle sensor 70 even when the tiltangle sensor 70 provided in the tilt bucket 8 cannot output accuratetilt angle data due to the attitude or the like of the bucket 8 isprovided. The tilt angle data is fixed according to the operation of theoperator based on the fixing command, whereby an excavation operationcan be performed accurately using the fixed data.

According to the present embodiment, the outer shape of the tilt bucket8 and the target excavation landform along the working plane MP whichserves as a control object of the limited excavation control can bespecified. Thus, even when the distance between the bucket 8 and thetarget excavation landform changes due to tilting of the bucket 8, it ispossible to perform limited excavation control with high accuracy sothat the bucket 8 does not dig into the target excavation landform.

In the present embodiment, the 2-dimensional bucket data indicating theouter shape of the bucket 8 in the working plane MP is calculated basedon the dimension data of the work machine 2, the shape data of thebucket 8, the work machine angle data, and the tilt angle data. Thus,even when the tilt angle of the bucket 8 changes, it is possible todetect the position of the cutting edge 8 a of the bucket 8 in theworking plane MP. Therefore, it is possible to detect the relativeposition between the cutting edge 8 a and the target excavation landformaccurately to execute intended construction while suppressing a decreasein the excavation accuracy.

In the present embodiment, the dimension data of the work machine 2, thetarget excavation landform data, and the work machine angle data areacquired, and the work machine control unit 26A determines the speedlimit according to the distance between the bucket 8 and the targetexcavation landform based on the target excavation landform data U andthe bucket position data and controls the work machine 2 so that thespeed in the direction in which the work machine 2 approaches the targetexcavation landform is equal to or smaller than the speed limit. Due tothis, the bucket 8 is suppressed from digging into the target excavationlandform and a decrease in excavation accuracy is suppressed.

In the present embodiment, the fixing command is output to the datafixing unit 28D so that the work machine 2 is controlled based on thefixed data in at least a portion of the limited excavation controlperiod. Thus, the tilt angle data is fixed based on the fixing command,and limited excavation control can be performed with high accuracy.

In the present embodiment, the fixing command is output to the datafixing unit 28D at the start of the limited excavation control and isdisabled at the end of the limited excavation control. Thus, limitedexcavation control is performed with high accuracy. In a normalexcavation operation, the excavation operation can be performed withoutfixing the tilt angle data.

In the present embodiment, in the limited excavation control, thedriving of the bucket 8 is inhibited by the driving inhibiting unit 26B,and the position of the bucket 8 in a rotation direction about the tiltshaft J4 as well as the tilt angle data are fixed. Thus, it is possibleto perform excavation while moving the bucket 8 along the targetexcavation landform.

In the present embodiment, since the driving inhibiting unit 26Bdisables the operation signal output from the operating device 25, it ispossible to smoothly inhibit the driving of the bucket 8.

In the present embodiment, the work machine 2 is controlled by the workmachine control unit 26A based on 2-dimensional bucket data. Due tothis, the work machine control unit 26A can derive the distance dbetween the bucket 8 and the target excavation landform based on the2-dimensional bucket data S and the target excavation landform along theworking plane MP and perform limited excavation control of the workmachine 2.

In the present embodiment, the relative position between the bucket 8and the target excavation landform is calculated based on the2-dimensional bucket data, the vehicle body position data P indicatingthe present position of the vehicle body 1, and the vehicle bodyattitude data Q indicating the attitude of the vehicle body 1. Due tothis, it is possible to calculate the accurate relative position betweenthe bucket 8 and the target excavation landform.

In the present embodiment, the target excavation landform data and thebucket position data are displayed on the display unit 26. Due to this,a control object is specified based on the working plane MP and thelimited excavation control is performed with high accuracy.

In the present embodiment, the vehicle body position data P and thevehicle body attitude data Q of the excavator CM in the globalcoordinate system are acquired, and the relative position between thebucket 8 and the target excavation landform in the global coordinatesystem is acquired using the position (2-dimensional bucket data S) ofthe bucket 8 calculated in the local coordinate system, the vehicle bodyposition data P, and the vehicle body attitude data Q. The targetexcavation landform data may be defined in the local coordinate systemand the relative position between the bucket 8 and the target excavationlandform in the local coordinate system may be acquired. The same istrue for the following embodiments.

In the present embodiment, the limited excavation control (interventioncontrol) is performed using the 2-dimensional bucket data S. The limitedexcavation control may not be performed. For example, the operator mayoperate the operating device 25 while monitoring the display unit 29 sothat the bucket 8 moves along the target excavation landform in theworking plane MP. The same is true for the following embodiments.

While the embodiments of the present invention have been described, thepresent invention is not limited to the embodiments and various changescan be made without departing from the spirit of the present invention.

In the above-described embodiments, although an excavator has beendescribed as an example of the construction machine, the constructionmachine is not limited to the excavator, and the present invention maybe applied to other types of construction machine.

The position of the excavator CM in the global coordinate system may beacquired by other position measurement means without being limited toGNSS. Thus, the distance d between the target excavation landform andthe cutting edge 8 a may be acquired by other position measurement meanswithout being limited to GNSS.

The amount of boom operation, the amount of arm operation, and theamount of bucket operation may be acquired based on an electrical signalindicating the position of the operating lever (25R and 25L).

REFERENCE SIGNS LIST

-   -   1 VEHICLE BODY    -   2 WORK MACHINE    -   3 REVOLVING STRUCTURE    -   4 CAB    -   5 TRAVELING DEVICE    -   5Cr CRAWLER BELT    -   6 BOOM    -   7 ARM    -   8 BUCKET    -   9 ENGINE ROOM    -   10 BOOM CYLINDER    -   11 ARM CYLINDER    -   12 BUCKET CYLINDER    -   13 BOOM PIN    -   14 ARM PIN    -   15 BUCKET PIN    -   16 FIRST STROKE SENSOR    -   17 SECOND STROKE SENSOR    -   18 THIRD STROKE SENSOR    -   19 HANDRAIL    -   20 POSITION DETECTION DEVICE    -   21 ANTENNA    -   22 ANGLE DETECTION DEVICE    -   23 POSITION SENSOR    -   24 INCLINATION SENSOR    -   25 OPERATING DEVICE    -   25F OPERATION PEDAL    -   25L SECOND OPERATING LEVER    -   25R FIRST OPERATING LEVER    -   25P THIRD OPERATING LEVER    -   26 WORK MACHINE CONTROLLER    -   27 CONTROL VALVE    -   28 DISPLAY CONTROLLER    -   29 DISPLAY UNIT    -   30 TILT CYLINDER    -   32 SENSOR CONTROLLER    -   36 INPUT UNIT    -   40A CAP-SIDE OIL CHAMBER    -   40B ROD-SIDE OIL CHAMBER    -   41 MAIN HYDRAULIC PUMP    -   42 PILOT HYDRAULIC PUMP    -   43 MAIN VALVE    -   51 SHUTTLE VALVE    -   70 TILT ANGLE SENSOR    -   80 TILT PIN    -   81 BOTTOM PLATE    -   82 BACK PLATE    -   83 TOP PLATE    -   84 SIDE PLATE    -   85 SIDE PLATE    -   86 OPENING    -   87 BRACKET    -   88 BRACKET    -   90 CONNECTION MEMBER    -   91 PLATE MEMBER    -   92 BRACKET    -   93 BRACKET    -   94 FIRST LINK MEMBER    -   94P FIRST LINK PIN    -   95 SECOND LINK MEMBER    -   95P SECOND LINK PIN    -   96 BUCKET CYLINDER TOP PIN    -   97 BRACKET    -   161 ROTATION ROLLER    -   162 ROTATION CENTER SHAFT    -   163 ROTATION SENSOR PORTION    -   164 CASE    -   200 CONTROL SYSTEM    -   300 HYDRAULIC SYSTEM    -   AX REVOLUTION AXIS    -   CM CONSTRUCTION MACHINE (EXCAVATOR)    -   J1 BOOM SHAFT    -   J2 ARM SHAFT    -   J3 BUCKET SHAFT    -   J4 TILT SHAFT    -   L1 BOOM LENGTH    -   L2 ARM LENGTH    -   L3 BUCKET LENGTH    -   L4 TILT LENGTH    -   L5 WIDTH DIMENSION OF BUCKET    -   P VEHICLE BODY POSITION DATA    -   Q VEHICLE BODY ATTITUDE DATA (REVOLVING STRUCTURE DIRECTION        DATA)    -   S 2-DIMENSIONAL BUCKET DATA    -   T TARGET CONSTRUCTION INFORMATION    -   U TARGET EXCAVATION LANDFORM DATA    -   α BOOM ANGLE    -   β ARM ANGLE    -   γ BUCKET ANGLE    -   δ TILT ANGLE    -   ε TILT SHAFT ANGLE

1. A construction machine control system for a construction machine thatincludes a work machine comprising: a boom capable of rotating inrelation to a vehicle body about a boom shaft; an arm capable ofrotating in relation to the boom about an arm shaft parallel to the boomshaft; and a bucket capable of rotating in relation to the arm abouteach of a bucket shaft parallel to the arm shaft and a tilt shaftorthogonal to the bucket shaft, the system comprising: a tilt anglesensor that is provided in the bucket so as to detect tilt angle dataincluding a rotation angle of the bucket about at least the tilt shaft,the tilt angle sensor being capable of detecting an inclination anglewith respect to a horizontal plane; a data acquisition unit to which thetilt angle data is output from the tilt angle sensor; a data fixing unitthat fixes the tilt angle data output to the data acquisition unit basedon a fixing command to generate fixed data; and a driving inhibitingunit that inhibits driving of the bucket in response to the fixingcommand.
 2. The construction machine control system according to claim1, further comprising: a first acquisition unit that acquires dimensiondata including dimensions of the boom, the arm, and the bucket; a secondacquisition unit that acquires target excavation landform dataindicating a target excavation landform which is a target shape of anexcavation object; a third acquisition unit that acquires work machineangle data including boom angle data indicating a rotation angle of theboom about the boom shaft, arm angle data indicating a rotation angle ofthe arm about the arm shaft, and bucket angle data indicating a rotationangle of the bucket about the bucket shaft; and a calculation unit thatcalculates bucket position data indicating a present position of thebucket based on the work machine angle data, the dimension data, and thefixed data, wherein the work machine control unit determines a speedlimit according to a distance between the bucket and the targetexcavation landform based on the target excavation landform data and thebucket position data and executes limited excavation control so that aspeed in a direction in which the work machine approaches the targetexcavation landform is equal to or smaller than the speed limit, and thefixing command is output to the data fixing unit so that the workmachine is controlled based on the fixed data in at least a portion of aperiod in which the limited excavation control is executed.
 3. Theconstruction machine control system according to claim 2, wherein thefixing command is output to the data fixing unit when the limitedexcavation control starts and is disabled when the limited excavationcontrol ends.
 4. (canceled)
 5. The construction machine control systemaccording to claim 1, further comprising: an operating device thatoutputs an operation signal for operating a hydraulic cylinder capableof driving the bucket, wherein the driving inhibiting unit disables theoperation signal output from the operating device.
 6. The constructionmachine control system according to claim 2, further comprising: afourth acquisition unit that acquires shape data of the bucket, whereinthe target excavation landform data is 2-dimensional target shape of theexcavation object in a working plane orthogonal to the bucket shaft, thecalculation unit calculates 2-dimensional bucket data which indicates anouter shape of the bucket in the working plane and includes the bucketposition data based on the work machine angle data, the dimension data,the shape data, and the fixed data, and the work machine control unitcontrols the work machine based on the 2-dimensional bucket data.
 7. Theconstruction machine control system according to claim 6, wherein thecalculation unit calculates a relative position between the bucket andthe target excavation landform based on the 2-dimensional bucket data,vehicle body position data indicating a present position of the vehiclebody, and vehicle body attitude data indicating an attitude of thevehicle body.
 8. A construction machine comprising: a lower travelingstructure; an upper revolving structure that is supported by the lowertraveling structure; a work machine that includes a boom, an arm and abucket and is supported by the upper revolving structure; and thecontrol system according to claim
 1. 9. A method of controlling aconstruction machine that includes a work machine comprising: a boomcapable of rotating in relation to a vehicle body about a boom shaft; anarm capable of rotating in relation to the boom about an arm shaftparallel to the boom shaft; and a bucket capable of rotating in relationto the arm about a bucket shaft parallel to the arm shaft and a tiltshaft orthogonal to the bucket shaft, the method comprising: detectingtilt angle data indicating a rotation angle of the bucket about the tiltshaft using a tilt angle sensor that is provided in the bucket and thatcan detect an inclination angle with respect to a horizontal plane;acquiring the tilt angle data output from the tilt angle sensor; fixingthe tilt angle data based on a fixing command to generate fixed data;and inhibiting driving of the bucket in response to the fixing command.